1
00:00:00,000 --> 00:00:12,610

2
00:00:12,610 --> 00:00:12,900
>> DAVID J. Malan: Kull dritt.

3
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Allura merħba lill-ewwel darba
Postmortem CS50 għal kwizz.

4
00:00:16,790 --> 00:00:18,340
Ħsibna aħna'd jinawgura
din it-tradizzjoni din is-sena.

5
00:00:18,340 --> 00:00:20,960
U dan se jkun opportunità
jimxu permezz tal-

6
00:00:20,960 --> 00:00:22,220
soluzzjonijiet għall-kwizz.

7
00:00:22,220 --> 00:00:26,160
U aħna ser tħaffef jew inaqqsu bbażati
fuq l-interess ta 'dawk hawn.

8
00:00:26,160 --> 00:00:29,730
>> Allura int probabilment hawn għax int
interessati dwar kif jista 'jkollok jew

9
00:00:29,730 --> 00:00:31,170
kellha wkoll tirrispondi xi
ta 'dawn il-problemi.

10
00:00:31,170 --> 00:00:33,300
Allura għaliex ma we tagħti ħarsa
fuq din it-taqsima l-ewwel?

11
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Allura jkollna kordi.

12
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Dan ħadt tliet verżjonijiet differenti
ta 'programm li kien, finalment,

13
00:00:37,600 --> 00:00:39,650
maħsuba biex tikseb string minn utent.

14
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Jew le ma li kien
xellug inti biex jiddeterminaw.

15
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>> U aħna mitluba fil-Mistoqsija 0,
jissoponi li Verżjoni 1 hija

16
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miġbura u esegwiti.

17
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Għaliex jista 'il-programm segfault?

18
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Ewwel daqqa t'għajn, kwalunkwe suġġerimenti
għaliex?

19
00:00:51,150 --> 00:00:54,012

20
00:00:54,012 --> 00:00:54,489
Yeah.

21
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>> UDJENZA: So I remember jaraw dan
eżempju preċedenti ta 'tħares lejn l-

22
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char * i u tara l-iskan ta 'l iu
jaraw għaliex dan huwa pointer, kif

23
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ma taffettwa dak li inti skanjata fil-?

24
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Huwa s jew l-indirizz ta 'i?

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>> DAVID J. Malan: OK.

26
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Tajba.

27
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Allura finalment, is-sors ta 'xi problema
huwa preżumibbilment se jitnaqqas

28
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għal dak il-varjabbli s.

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U huwa tabilħaqq varjabbli.

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Dejta tat-tip ta 'dak il-varjabbli huwa
char *, li jfisser li għaddej biex

31
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fihom l-indirizz ta 'karattru.

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U fih tinsab l-għarfien.

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Huwa ser jinkludi l-indirizz ta '
karattru jew, b'mod aktar ġenerali, il-

34
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indirizz ta 'l-ewwel karattru
blokk kollu ta 'karattri.

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>> Iżda l-qabda hija li scan s, skop
ħajja, huwa jingħata indirizz u mogħtija

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kodiċi format, bħal% s, moqri
string fil-blokki ta '

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memorja f'dak l-indirizz.

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Iżda għaliex hemm l-ebda sinjal ugwali quddiem
li semicolon fl-ewwel

39
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linja tal-kodiċi, għaliex aħna ma attwalment
jalloka memorja ma

40
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malloc, għaliex hija ma attwalment
talloka firxa ta 'ċertu daqs, kollha

41
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qed tagħmel huwa qari tal-l-utent
input keyboard fis xi kompluta

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valur żibel, li
huwa s-kontumaċja.

43
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Allura odds huma int ser segfault jekk
dak l-indirizz ma biss hekk jiġri

44
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li tkun valur li inti tista ',
fil-fatt, jikteb lill.

45
00:02:08,009 --> 00:02:10,889
Daqshekk ħżiena li ma tallokax
memorja tiegħek hemmhekk.

46
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>> Allura fid-domanda 1, staqsejna,
jissoponi li verżjoni 2 hija

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miġbura u esegwiti.

48
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Għaliex jista 'dan il-programm segfault?

49
00:02:15,900 --> 00:02:17,990
Allura dan huwa wieħed inqas Buggy.

50
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U hemm verament biss wieħed
mod ovvju fejn tista '

51
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jikkawżaw segfault hawn.

52
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U dan huwa tematika.

53
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Kwalunkwe ħin aħna qed jużaw c fil-memorja, liema
inti tista 'tagħmel biex jinduċi segfault

54
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mal-verżjoni 2?

55
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>> UDJENZA: Jekk tuża dan input
string li l-itwal minn 49

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karattri.

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>> DAVID J. Malan: Eżattament.

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Kwalunkwe ħin li inti tara xi ħaġa fiss tul
meta niġu għall-firxa, tiegħek

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radar għandhom imorru off li dan jista 'jkun
problematika jekk int ma iċċekkjar tal-

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konfini ta 'firxa.

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U li l-problema hawnhekk.

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Aħna qed għadhom jużaw scanf.

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Aħna qed għadhom jużaw% s, li jfisser jippruvaw
biex jaqra string mill-utent.

64
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Li għaddej biex jinqraw fis s, li,
f'dan il-punt, huwa effettivament il-

65
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indirizz ta 'blokki ta' memorja
jew huwa ekwivalenti.

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Hu l-isem ta 'firxa
ta 'karattri ta' memorja.

67
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>> Imma eżattament dan, jekk inti taqra string
dan huwa itwal minn 49 karattri, 49

68
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għaliex għandek bżonn spazju għall-backslash
0, int ser jfur

69
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li buffer.

70
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U inti tista 'tikseb xortik tajba u tkun tista'
jiktbu karattru 51, 52, 53.

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Iżda f'xi punt, l-OS
se ngħid, no.

72
00:03:18,560 --> 00:03:21,270
Dan żgur m'huwiex memorja
int permess tmissx.

73
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U l-programm se segfault.

74
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>> Allura hemm, il-heuristics għandu jkun kwalunkwe
ħin li inti stajt ltqajna tul fiss, għandek

75
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tagħmel żgur li int iċċekkjar it-tul
ta 'kwalunkwe huwa inti qed tipprova

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biex jinqara fis dan.

77
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>> UDJENZA: Allura biex issolvi dan, inti tista '
kellhom dikjarazzjoni verifika attwalment

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huwa l-aktar fit-tul
jew inqas minn?

79
00:03:37,140 --> 00:03:37,730
>> DAVID J. Malan: Assolutament.

80
00:03:37,730 --> 00:03:41,706
Inti sempliċiment għandek kundizzjoni
li tgħid, jekk il -

81
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jew pjuttost inti ma neċessarjament jaf
bil-quddiem kemm-karattri l-

82
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utent se tip, għaliex
għandek tiġieġ u l-bajd.

83
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Mhux sakemm inti stajt taqrah ma scanf
inti tista 'figura kemm żmien huwa.

84
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Iżda f'dak il-punt, huwa tard wisq,
għaliex inti stajt diġà taqraha fis

85
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xi blokk ta 'memorja.

86
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Allura Bħala twarrib, il jevita librerija CS50
din il-kwistjoni għal kollox, recall

87
00:03:59,590 --> 00:04:01,060
bl-użu fgetc.

88
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U jgħid karattru wieħed fi żmien,
flimkien, jafu toeing-ponta li inti

89
00:04:05,390 --> 00:04:08,060
ma tistax overflow karattru jekk
inti taqra wieħed kull darba.

90
00:04:08,060 --> 00:04:11,580
>> Il-qabda hija ma recall getstring huwa
li għandna kontinwament daqs ri

91
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li blokki ta 'memorja, li
huwa biss uġigħ.

92
00:04:13,590 --> 00:04:15,310
Huwa ħafna ta 'linji ta'
kodiċi sabiex tagħmel dan.

93
00:04:15,310 --> 00:04:18,779
Allura approċċ ieħor ikun li
attwalment jużaw ku, hekk

94
00:04:18,779 --> 00:04:19,790
biex jitkellmu, ta scanf.

95
00:04:19,790 --> 00:04:22,820
Hemm varjanti ta 'lott ta' dawn
funzjonijiet li attwalment jikkontrollaw l-

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tul ta 'kif ħafna karattri
inti tista 'taqra maximally.

97
00:04:25,870 --> 00:04:29,430
U inti tista 'tispeċifika, ma taqra
aktar minn 50 karattru.

98
00:04:29,430 --> 00:04:34,110
Allura li jkun approċċ ieħor iżda
inqas akkomodazzjoni ta 'inputs akbar.

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>> Allura mistoqsija 2 tistaqsi, jissoponi li verżjoni
3 hija miġbura u esegwiti.

100
00:04:37,040 --> 00:04:39,960
Għaliex jista 'dak il-programm segfault?

101
00:04:39,960 --> 00:04:42,650
Allura dan huwa wieħed attwalment l-istess
tingħata risposta, anki jekk

102
00:04:42,650 --> 00:04:43,590
jistenna ftit fancier.

103
00:04:43,590 --> 00:04:46,440
Aħna qed tuża malloc, li jħoss simili
aħna qed jagħtu lilna nfusna aktar għażliet.

104
00:04:46,440 --> 00:04:48,030
U allura aħna qed ħelsien li
memorja fl-aħħar.

105
00:04:48,030 --> 00:04:49,580
Huwa għadu biss 50 bytes ta 'memorja.

106
00:04:49,580 --> 00:04:53,620
Allura aħna xorta tista 'tipprova li jaqra
f'51, 52, 1,000 bytes.

107
00:04:53,620 --> 00:04:55,830
Li għaddej biex segfault għal
eżattament l-istess raġuni.

108
00:04:55,830 --> 00:04:57,530
>> Iżda hemm raġuni oħra wisq.

109
00:04:57,530 --> 00:05:03,890
X'aktar jista malloc ritorn minbarra
l-indirizz ta 'blokki ta' memorja?

110
00:05:03,890 --> 00:05:04,920
Dan jista 'ritorn null.

111
00:05:04,920 --> 00:05:07,560
U għaliex aħna mhux qed iċċekkjar għall-
dan, aħna jista 'jkun tagħmel xi ħaġa

112
00:05:07,560 --> 00:05:11,350
stupid għal raġuni oħra, li huwa li
aħna jista 'jkun javżak scanf, moqri

113
00:05:11,350 --> 00:05:16,050
input tal-utent mill-keyboard
fis 0 lokazzjoni, null AKA.

114
00:05:16,050 --> 00:05:18,890
U li, wisq, definittivament se
jikkawżaw segfault.

115
00:05:18,890 --> 00:05:21,590
Allura għall-iskop tal-kwizz, aħna kieku
aċċettaw jew ta 'dawk bħala

116
00:05:21,590 --> 00:05:22,740
raġuni valida.

117
00:05:22,740 --> 00:05:23,420
Wieħed huwa identiku.

118
00:05:23,420 --> 00:05:25,720
Wieħed huwa xi ftit aktar sfumata.

119
00:05:25,720 --> 00:05:28,975
>> Fl-aħħar nett, rigward il-tal-programm
użu tal-memorja, kif do verżjoni 2 u

120
00:05:28,975 --> 00:05:30,350
Verżjoni 3 differenti?

121
00:05:30,350 --> 00:05:35,070
Allura għal dak li hi ta 'valur, rajna
provvista donnu ma jieqaf ta 'possibbli

122
00:05:35,070 --> 00:05:35,770
tweġibiet għal dan.

123
00:05:35,770 --> 00:05:39,300
U fost tweġibiet tan-nies, dak li konna
bit-tama għal, iżda aħna aċċettati oħra

124
00:05:39,300 --> 00:05:42,250
affarijiet, kien xi referenza għall-
fatt li verżjoni 2 qed tuża

125
00:05:42,250 --> 00:05:44,560
l-hekk imsejħa munzell.

126
00:05:44,560 --> 00:05:46,710
Verżjoni 3 qed tuża l-borġ.

127
00:05:46,710 --> 00:05:50,060
U funzjonalment, dan ma verament
jagħmlu dak kollu li ħafna ta 'differenza.

128
00:05:50,060 --> 00:05:54,040
Fl-aħħar tal-ġurnata, aħna qed għadhom
biss jkollna 50 bytes ta 'memorja.

129
00:05:54,040 --> 00:05:56,640
>> Iżda dan kien wieħed mis-soluzzjonijiet possibbli
li konna tħares lejn.

130
00:05:56,640 --> 00:05:59,730
Imma int ser tara, kif ikollok kwizzijiet tiegħek
lura mill-TFS, li għamilna

131
00:05:59,730 --> 00:06:04,330
jaċċettaw diskussjonijiet oħra ta 'tagħhom
użi differenti tal-memorja kif ukoll.

132
00:06:04,330 --> 00:06:08,600
Iżda munzell u borġ kien ikun
tweġiba faċli li jmorru magħhom.

133
00:06:08,600 --> 00:06:11,150
Kwalunkwe mistoqsijiet?

134
00:06:11,150 --> 00:06:12,400
I jagħtuk Rob.

135
00:06:12,400 --> 00:06:18,360

136
00:06:18,360 --> 00:06:20,210
>> ROB BOWDEN: Allura problema 4.

137
00:06:20,210 --> 00:06:21,985
Dan huwa dak fejn kellek li timla
fin-numru ta 'bytes barra minn kull

138
00:06:21,985 --> 00:06:23,460
dawn it-tipi differenti użati.

139
00:06:23,460 --> 00:06:24,830
Allura l-ewwel ħaġa li naraw.

140
00:06:24,830 --> 00:06:27,930
Assumi arkitettura 32-bit,
bħal dan appliance CS50.

141
00:06:27,930 --> 00:06:33,530
Allura waħda mill-affarijiet fundamentali dwar
Arkitetturi 32-bit, li tgħidilna

142
00:06:33,530 --> 00:06:37,490
eżattament kif big a pointer huwa għaddej
li jkun fl-arkitettura.

143
00:06:37,490 --> 00:06:43,020
>> Allura immedjatament, nafu li kull pointer
tip huwa 32-bits jew 4 bytes.

144
00:06:43,020 --> 00:06:46,010
Allura tħares lejn din it-tabella, a
node * huwa tip pointer.

145
00:06:46,010 --> 00:06:47,250
Li għaddej biex jkun ta '4 bytes.

146
00:06:47,250 --> 00:06:51,640
Node Struct *, li litteralment
identika għal star node.

147
00:06:51,640 --> 00:06:53,590
U hekk li għaddej biex jkun ta '4 bytes.

148
00:06:53,590 --> 00:06:58,270
String, u għalhekk ma look like a
pointer s'issa, iżda l-typedef, a

149
00:06:58,270 --> 00:07:01,590
string huwa biss char a *, li
huwa tip pointer.

150
00:07:01,590 --> 00:07:03,550
Allura li għaddej biex jkun ta '4 bytes.

151
00:07:03,550 --> 00:07:06,150
>> Allura dawn it-tlieta huma 4 bytes kollha.

152
00:07:06,150 --> 00:07:09,350
Issa, node u student huma
daqsxejn aktar ikkumplikata.

153
00:07:09,350 --> 00:07:15,160
Allura tħares lejn node u student, naraw
node bħala numru sħiħ u pointer.

154
00:07:15,160 --> 00:07:18,050
U student huwa żewġ pointers
ġewwa ta 'dan.

155
00:07:18,050 --> 00:07:23,340
Dan bl-inqas għall-każ tagħna hawn, il-mod
li aħna jispiċċaw kalkolu tad-daqs tal-

156
00:07:23,340 --> 00:07:27,020
din Struct huwa biss jammontaw kollox
dan huwa ġewwa l-Struct.

157
00:07:27,020 --> 00:07:30,690
>> Allura għal node, għandna integer,
li huwa 4 bytes.

158
00:07:30,690 --> 00:07:32,830
Għandna pointer, li huwa 4 bytes.

159
00:07:32,830 --> 00:07:35,820
U għalhekk node wieħed ikun ser
li jibdew 8 bytes.

160
00:07:35,820 --> 00:07:39,490
U l-istess għall-istudenti, għandna
pointer li l-4 bytes u ieħor

161
00:07:39,490 --> 00:07:40,770
pointer li l-4 bytes.

162
00:07:40,770 --> 00:07:43,180
Allura li għaddej biex tintemm
jiddiżappuntaw 8 bytes.

163
00:07:43,180 --> 00:07:45,480
Allura node u student huma 8 bytes.

164
00:07:45,480 --> 00:07:48,950
U dawn it-tliet huma 4 bytes kollha.

165
00:07:48,950 --> 00:07:50,240
Mistoqsijiet dwar li?

166
00:07:50,240 --> 00:07:54,640

167
00:07:54,640 --> 00:07:54,990
Iva.

168
00:07:54,990 --> 00:07:58,413
>> UDJENZA: Huwa kien 64-bit
arkitettura, kieku dik

169
00:07:58,413 --> 00:07:59,880
tirdoppja kull wieħed minnhom?

170
00:07:59,880 --> 00:08:01,790
>> ROB BOWDEN: ma jkunx
tirdoppja kull wieħed minnhom.

171
00:08:01,790 --> 00:08:05,830
Allura arkitettura 64-bit, huwa, għal darb'oħra,
bidliet li ħaġa fundamentali li

172
00:08:05,830 --> 00:08:08,910
pointer issa huwa 64 bits.

173
00:08:08,910 --> 00:08:09,290
Yeah.

174
00:08:09,290 --> 00:08:10,930
Allura pointer huwa 8 bytes.

175
00:08:10,930 --> 00:08:15,420
Allura dawn li kienu 4 bytes
ser ikunu 8 bytes.

176
00:08:15,420 --> 00:08:18,617
Student, li kien żewġ pointers,
ukoll, issa li għaddej biex

177
00:08:18,617 --> 00:08:19,800
jkun 8 bytes, 8 bytes.

178
00:08:19,800 --> 00:08:21,980
Huwa ser jagħmlu 16 bytes.

179
00:08:21,980 --> 00:08:25,710
>> Iżda node xorta huwa 4 bytes.

180
00:08:25,710 --> 00:08:27,800
Allura dan il-werrej huwa għaddej
li jkun 8 bytes.

181
00:08:27,800 --> 00:08:28,930
Dan huwa 4 bytes.

182
00:08:28,930 --> 00:08:30,870
Allura node huwa biss se
li jkun ta '12 bytes.

183
00:08:30,870 --> 00:08:36,309

184
00:08:36,309 --> 00:08:39,280
Kwalunkwe mistoqsijiet oħra fuq li wieħed?

185
00:08:39,280 --> 00:08:44,500
Allura dak li jmiss, dawn huma
il-kodiċijiet ta 'stat HTTP.

186
00:08:44,500 --> 00:08:48,000
U kellek biex tiddeskrivi ċ-ċirkostanzi
li taħthom dawn jistgħu

187
00:08:48,000 --> 00:08:49,810
jiġu rritornati lilek.

188
00:08:49,810 --> 00:08:56,730
problema waħda li smajt xi studenti
għandhom hija li huma ppruvaw jagħmlu l-

189
00:08:56,730 --> 00:08:58,950
żbalji jkun fuq il-għan tal-klijent.

190
00:08:58,950 --> 00:09:02,320
Allura meta aħna nippruvaw nagħmlu t-talba
għall-server, xi ħaġa tmur

191
00:09:02,320 --> 00:09:03,820
ħażin fuq il-għan tagħna.

192
00:09:03,820 --> 00:09:07,660
Iżda ġeneralment, dawn il-kodiċijiet huma
jkun mibgħut lura mill-server.

193
00:09:07,660 --> 00:09:11,720
Hekk irridu insemmu x'inhu għaddej
żbaljata jew dritt fuq il-server li

194
00:09:11,720 --> 00:09:14,280
tikkawża dawn l-affarijiet jiġu rritornati.

195
00:09:14,280 --> 00:09:18,670
Allura għaliex jista 'server prospetti
kodiċi istat 200?

196
00:09:18,670 --> 00:09:19,920
Kwalunkwe ħsibijiet?

197
00:09:19,920 --> 00:09:23,360

198
00:09:23,360 --> 00:09:23,730
>> Yeah.

199
00:09:23,730 --> 00:09:27,850
Allura xi ħaġa dwar b'suċċess
it-talba għaddiet.

200
00:09:27,850 --> 00:09:30,260
U dawn qed kapaċi li jirritornaw
x'ikun inti mitlub.

201
00:09:30,260 --> 00:09:32,240
Hekk kollox kien multa.

202
00:09:32,240 --> 00:09:35,662
What about 302 misjuba?

203
00:09:35,662 --> 00:09:36,618
Yeah.

204
00:09:36,618 --> 00:09:39,008
>> UDJENZA: Il-server kien qed ifittex
għal dak li inti mitlub.

205
00:09:39,008 --> 00:09:40,442
Iżda ma setgħetx issib lilha.

206
00:09:40,442 --> 00:09:42,850
Allura hemm żball.

207
00:09:42,850 --> 00:09:47,720
>> ROB BOWDEN: Allura l-server kien
tfittex dak li riedu.

208
00:09:47,720 --> 00:09:51,682
Hekk biss tfittex hawn, 302 misjuba,
hija kienet f'pożizzjoni li jsibuha.

209
00:09:51,682 --> 00:09:53,035
>> UDJENZA: Jien sorry.

210
00:09:53,035 --> 00:09:54,388
Misjuba ifisser li huma għamlu jsibuha.

211
00:09:54,388 --> 00:09:55,638
Jiddispjacini.

212
00:09:55,638 --> 00:09:58,120

213
00:09:58,120 --> 00:10:00,160
>> ROB BOWDEN: So 302 misjuba.

214
00:10:00,160 --> 00:10:02,350
Il-server huwa kapaċi li jsibu
dak li riedu.

215
00:10:02,350 --> 00:10:04,640
>> UDJENZA: Imma din mhix l-wiri?

216
00:10:04,640 --> 00:10:08,180
>> ROB BOWDEN: Id-differenza bejn
dan 302 u 200 huwa li

217
00:10:08,180 --> 00:10:09,280
jaf dak li trid.

218
00:10:09,280 --> 00:10:12,000
Iżda mhuwiex eżattament fejn
inti ridt li jistaqsu.

219
00:10:12,000 --> 00:10:14,580
Allura 302 hija direzzjoni ġdida tipiku.

220
00:10:14,580 --> 00:10:16,510
Allura inti mitlub paġna.

221
00:10:16,510 --> 00:10:19,590
Huwa jaf, oh, I jridu
li inti tirritorna dan.

222
00:10:19,590 --> 00:10:21,070
Iżda dan huwa bi URL differenti.

223
00:10:21,070 --> 00:10:23,534
Allura ħej, inti fil-fatt tixtieq dan.

224
00:10:23,534 --> 00:10:26,950
>> DAVID J. Malan: Huwa biċċa li qal
li aħna taw inti guys direzzjoni ġdida

225
00:10:26,950 --> 00:10:30,830
funzjoni li jintuża l-funzjoni header
li, imbagħad, stampata post,

226
00:10:30,830 --> 00:10:34,110
kolon, u allura l-URL li
inti tixtieq li tirrifjuta l-utent.

227
00:10:34,110 --> 00:10:37,480
Anke jekk inti ma tara 302
espliċitu hemmhekk, dan huwa dak PHP

228
00:10:37,480 --> 00:10:41,550
se magically daħħal l-header
tgħid eżattament dak li Rob qal hemm -

229
00:10:41,550 --> 00:10:41,930
misjuba.

230
00:10:41,930 --> 00:10:43,180
Iżda mur hawn minflok.

231
00:10:43,180 --> 00:10:45,960

232
00:10:45,960 --> 00:10:46,160
>> ROB BOWDEN: OK.

233
00:10:46,160 --> 00:10:47,630
Allura dak dwar 403 pprojbit?

234
00:10:47,630 --> 00:10:52,240

235
00:10:52,240 --> 00:10:57,120
>> UDJENZA: Naħseb li huwa li s-server
hija bażikament tgħid li l-klijent

236
00:10:57,120 --> 00:10:59,970
ma jistgħux jaċċessaw il-home page.

237
00:10:59,970 --> 00:11:03,260
>> ROB BOWDEN: Allura iva.

238
00:11:03,260 --> 00:11:07,670
Ukoll, ir-risposta tipiċi konna
jistennew xi ħaġa simili, il-fajls

239
00:11:07,670 --> 00:11:08,920
mhumiex chmodded xieraq.

240
00:11:08,920 --> 00:11:11,590
Li probabbilment taħt liema ċirkostanzi
inti raw lilhom.

241
00:11:11,590 --> 00:11:18,920
Iżda hemm raġuni li l-klijent
jista 'jkun tort hawn.

242
00:11:18,920 --> 00:11:20,440
Hemm attwalment kodiċi ieħor status -

243
00:11:20,440 --> 00:11:21,210
401.

244
00:11:21,210 --> 00:11:22,820
Allura dawn huma simili ħafna.

245
00:11:22,820 --> 00:11:24,590
>> 401 hija mhux awtorizzat.

246
00:11:24,590 --> 00:11:26,130
U 403 huwa pprojbit.

247
00:11:26,130 --> 00:11:31,890
U għalhekk mhux awtorizzat inti esklussivament
nikseb jekk int ma logged pulzieri

248
00:11:31,890 --> 00:11:34,520
Iżda qtugħ fil jista 'jfisser
li inti huma awtorizzati.

249
00:11:34,520 --> 00:11:37,930
Imma jekk int diġà illoggjat u int
xorta ma jkollhomx permess, imbagħad

250
00:11:37,930 --> 00:11:40,140
inti tista 'wkoll tikseb pprojbit.

251
00:11:40,140 --> 00:11:45,320
Mela jekk inti illoggjat u ma jkollhom
permess, projbiti wkoll

252
00:11:45,320 --> 00:11:47,164
xi ħaġa li tista 'tikseb.

253
00:11:47,164 --> 00:11:48,900
>> DAVID J. Malan: U l-mekkaniżmu
li dawn il-problemi huma normalment

254
00:11:48,900 --> 00:11:53,100
solvuti fuq is-server huwa
via liema kmand?

255
00:11:53,100 --> 00:11:57,700
Chmod, jekk huwa, tabilħaqq, permessi
joħroġ fuq il-fajl jew direttorju.

256
00:11:57,700 --> 00:11:59,220
>> ROB BOWDEN: Imbagħad 404 ma nstabx.

257
00:11:59,220 --> 00:12:03,100

258
00:12:03,100 --> 00:12:03,470
Yeah.

259
00:12:03,470 --> 00:12:10,150
Allura b'differenza 302 fejn ma kienx eżattament
fejn int tistaqsi imma jaf liema

260
00:12:10,150 --> 00:12:12,710
tixtieq, dan, hija biss għandha
ebda idea dak li trid.

261
00:12:12,710 --> 00:12:15,648
U inti ma jitlob
xi ħaġa valida.

262
00:12:15,648 --> 00:12:18,580

263
00:12:18,580 --> 00:12:22,310
418 jien teapot u mbagħad
500 server intern.

264
00:12:22,310 --> 00:12:24,870
Allura għaliex jista 'ikollok dan?

265
00:12:24,870 --> 00:12:26,120
>> Allura segfault -

266
00:12:26,120 --> 00:12:28,760

267
00:12:28,760 --> 00:12:30,640
I attwalment ma jafux il-gradazzjoni
standard għal din.

268
00:12:30,640 --> 00:12:34,850
Iżda jekk il-kodiċi PHP tiegħek kienet xi ħaġa
ħażin fiha, fit-teorija, din tista '

269
00:12:34,850 --> 00:12:39,650
attwalment segfault, f'liema każ, dan
500 żball server intern, xi ħaġa

270
00:12:39,650 --> 00:12:41,400
li hu ħażin ma 'l server tiegħek
konfigurazzjoni.

271
00:12:41,400 --> 00:12:44,320
Jew hemm żball sintassi
fil-kodiċi PHP tiegħek.

272
00:12:44,320 --> 00:12:46,095
Jew xi ħaġa ħażina li qed jiġri.

273
00:12:46,095 --> 00:12:48,320
>> DAVID J. Malan: Aħna ma tara segfault
fost tweġibiet ftit tan-nies.

274
00:12:48,320 --> 00:12:49,490
U teknikament, jista 'jiġri.

275
00:12:49,490 --> 00:12:53,820
Iżda li tkun PHP, il-programm
miktuba minn nies oħra, attwalment

276
00:12:53,820 --> 00:12:57,790
segfaulted, li biss jekk dawk il-persuni
invitat up u kiteb kodiċi Buggy fl

277
00:12:57,790 --> 00:13:00,680
interpretu tagħhom kieku
PHP innifsu segfault.

278
00:13:00,680 --> 00:13:06,460
Allura anke jekk 500 huwa bħal segfault
fl-ispirtu, huwa kważi dejjem l-

279
00:13:06,460 --> 00:13:10,490
riżultat ta 'kwistjoni fajl konfigurazzjoni
ma 'web server tiegħek jew, kif Rob imsemmi,

280
00:13:10,490 --> 00:13:13,200
żball sintassi, bħalek
ma jagħlqu kwotazzjoni.

281
00:13:13,200 --> 00:13:16,180
Jew int mitluf virgola x'imkien.

282
00:13:16,180 --> 00:13:23,677
>> UDJENZA: Dan għall-pset Shuttle, I
jaħsbu meta I ma kien darba I għafast il-

283
00:13:23,677 --> 00:13:26,300
browser, iżda xejn daħal up,
dak li jissejjaħ paġna abjad.

284
00:13:26,300 --> 00:13:28,056
Iżda kien minħabba l-kodiċi.

285
00:13:28,056 --> 00:13:29,440
Naħseb li kien JavaScript, right?

286
00:13:29,440 --> 00:13:29,770
>> ROB BOWDEN: Yeah.

287
00:13:29,770 --> 00:13:31,180
>> UDJENZA: Would dan l-iżball
xorta toħroġ?

288
00:13:31,180 --> 00:13:34,290
>> ROB BOWDEN: Allura inti ma gotten
dan l-iżball għaliex kollox

289
00:13:34,290 --> 00:13:36,930
mill-perspettiva tal-web server
kien kompletament multa.

290
00:13:36,930 --> 00:13:39,090
Imma inti mitlub index.html.

291
00:13:39,090 --> 00:13:42,000
Inti mitlub shuttle.js
u service.js.

292
00:13:42,000 --> 00:13:44,580
U kien kapaċi b'suċċess jirritornaw
lilek kollha ta 'dawk l-affarijiet -

293
00:13:44,580 --> 00:13:44,980
200.

294
00:13:44,980 --> 00:13:45,680
OK.

295
00:13:45,680 --> 00:13:49,330
Huwa biss meta browser tiegħek ppruvaw
tinterpreta l-kodiċi JavaScript li

296
00:13:49,330 --> 00:13:51,370
Huwa simili, stenna, dan mhuwiex
żball JavaScript valida.

297
00:13:51,370 --> 00:13:55,720

298
00:13:55,720 --> 00:13:58,210
Kwalunkwe mistoqsijiet oħra?

299
00:13:58,210 --> 00:14:00,750
Kull dritt.

300
00:14:00,750 --> 00:14:04,120
>> DAVID J. Malan: Allura li jmiss
up kien numru 11.

301
00:14:04,120 --> 00:14:07,610
U 11 kienet l-scariest
għal ħafna nies.

302
00:14:07,610 --> 00:14:14,620

303
00:14:14,620 --> 00:14:18,570
Allura l-aktar ħaġa importanti li wieħed jinnota hawnhekk
kienet li dan kien, fil-fatt, dwar

304
00:14:18,570 --> 00:14:19,840
lista marbuta doppjament.

305
00:14:19,840 --> 00:14:23,160
Iżda dan ma kienx l-istess bħal tas-sena loħra
problema lista marbuta doppjament,

306
00:14:23,160 --> 00:14:27,170
li ma jagħtuk l-twiddiba li
il-lista tista ', fil-fatt, tkun mhux magħżul.

307
00:14:27,170 --> 00:14:29,640
>> Allura l-fatt li l-lista kienet mhux magħżul
u l-fatt li din il-kelma kienet

308
00:14:29,640 --> 00:14:32,930
li enfasizzat hemm kienet maħsuba biex twassal
li dan huwa effettivament simplifikazzjoni

309
00:14:32,930 --> 00:14:35,430
ta 'dak li kieku kien ikun
problema aktar ta 'sfida

310
00:14:35,430 --> 00:14:36,600
u wieħed itwal.

311
00:14:36,600 --> 00:14:40,760
Allura żball komuni hawn kien li poġġew
Soluzzjoni tas-sena loħra fuq waħda tiegħek

312
00:14:40,760 --> 00:14:45,580
pager u mbagħad biss bl-addoċċ kopja li
stabbiliti bħala r-risposta, li huwa d-dritt

313
00:14:45,580 --> 00:14:48,520
twieġeb għal mistoqsija differenti
simili fl-ispirtu.

314
00:14:48,520 --> 00:14:51,340
Iżda l-irqaqat hawn
kienu kif ġej.

315
00:14:51,340 --> 00:14:55,200
>> Allura wieħed, aħna għandna node dikjarati u
definit fil-mod tas-soltu hawnhekk.

316
00:14:55,200 --> 00:14:59,230
Imbagħad aħna lista definita ta 'jkun globali
pointer initialized li null.

317
00:14:59,230 --> 00:15:02,150
Imbagħad apparentement, hemm żewġ funzjonijiet
għandna prototipi għall hawn, daħħal

318
00:15:02,150 --> 00:15:03,240
u neħħi.

319
00:15:03,240 --> 00:15:06,600
U allura aħna għandna xi kodiċi tal-kampjun hawn
jagħmlu mazz ta 'inserzjonijiet.

320
00:15:06,600 --> 00:15:09,930
U allura aħna nitolbuk biex jitlesta l-
implimentazzjoni tal daħħal hawn taħt f'tali

321
00:15:09,930 --> 00:15:14,380
b'mod li huwa introduċa n fil-lista
fil-ħin kostanti, enfasizza wkoll,

322
00:15:14,380 --> 00:15:15,730
anki jekk diġà preżenti.

323
00:15:15,730 --> 00:15:20,600
>> Allura l-sbuħija li tkun tista 'daħħal
fil-ħin kostanti huwa li jimplika

324
00:15:20,600 --> 00:15:23,060
li inti għandek daħħal
l-node ġdid fejn?

325
00:15:23,060 --> 00:15:23,690
Fil-faċċata.

326
00:15:23,690 --> 00:15:27,760
Għalhekk jelimina, B'xorti tajba, għall-inqas
wieħed mill-każijiet li jintużaw biex jeħtieġu

327
00:15:27,760 --> 00:15:30,520
saħansitra aktar linji ta 'kodiċi, bhalu għamlet
aħħar sena u anke fil-klassi meta aħna

328
00:15:30,520 --> 00:15:34,040
tkellem permezz ta 'dan it-tip ta' ħaġa
mal-bnedmin u ma 'xi

329
00:15:34,040 --> 00:15:35,250
kodiċi psewdo verbali.

330
00:15:35,250 --> 00:15:39,190
Allura fis-soluzzjoni hawn, ejja skip fuq
għal dak biss li jkollhom fuq viżwali

331
00:15:39,190 --> 00:15:40,480
l-iskrin.

332
00:15:40,480 --> 00:15:42,230
>> Avviż li aħna qed tagħmel dan li ġej.

333
00:15:42,230 --> 00:15:45,140
U wkoll avviż-simplifikazzjonijiet oħrajn
kienet li anke jekk huwa

334
00:15:45,140 --> 00:15:48,280
diġà preżenti, għalhekk dan ifisser li anki jekk
in-numru huwa diġà hemm, inti tista '

335
00:15:48,280 --> 00:15:50,280
biss bl-addoċċ daħħal ieħor
kopja ta 'dan.

336
00:15:50,280 --> 00:15:52,560
U li, wisq, kien intenzjonat li jkun
simplifikazzjoni, sabiex inti tista '

337
00:15:52,560 --> 00:15:54,940
tiffoka fuq, verament, xi wħud mill-aktar
parti intellettwalment interessanti u

338
00:15:54,940 --> 00:15:58,090
mhux biss xi żball kkontrollar addizzjonali
minħabba ż-żmien limitat.

339
00:15:58,090 --> 00:16:02,880
>> Allura f'dan il-soluzzjoni tal-kampjun, aħna jallokaw
a pointer fuq il-naħa tax-xellug

340
00:16:02,880 --> 00:16:04,510
ġenb hawn biex node.

341
00:16:04,510 --> 00:16:07,190
Issa, jirrealizzaw li pointer, kif
Rob qal, huwa biss 32 bits.

342
00:16:07,190 --> 00:16:09,060
U din attwalment ma fihom
indirizz sakemm inti

343
00:16:09,060 --> 00:16:09,970
tassenja din il indirizz.

344
00:16:09,970 --> 00:16:13,220
U nagħmlu dan fuq il-lemin
naħa via malloc.

345
00:16:13,220 --> 00:16:16,550
Bħal ċittadin tajba, aħna jivverifikaw li
malloc mhuwiex, fil-fatt, null, sabiex

346
00:16:16,550 --> 00:16:18,690
aħna ma joħolqu aċċidentalment
a segfault hawn.

347
00:16:18,690 --> 00:16:22,840
U kull darba li tuża malloc fil-ħajja, inti
għandu jiġi verifikat għal null, lest

348
00:16:22,840 --> 00:16:24,090
għandek bug sottili.

349
00:16:24,090 --> 00:16:28,460
>> Imbagħad aħna initialize li null minn
tassenja n u Preċedenti u li jmiss.

350
00:16:28,460 --> 00:16:32,450
U f'dan il-każ hawnhekk, I initialized
preċedenti li null, għaliex dan ġdida

351
00:16:32,450 --> 00:16:34,780
node se tkun l-ġodda
bidu tal-lista tiegħi.

352
00:16:34,780 --> 00:16:37,050
Allura hemm għaddej li jkun
xejn quddiemha.

353
00:16:37,050 --> 00:16:42,010
U nixtieq li tehmeż essenzjalment l-
lista eżistenti għall-node ġdid billi

354
00:16:42,010 --> 00:16:44,700
iffissar li jmiss ugwali għall-lista innifsu.

355
00:16:44,700 --> 00:16:47,120
Imma jien ma jsirx għadha biss.

356
00:16:47,120 --> 00:16:51,780
Allura jekk il-lista nnifisha diġà kienu jeżistu,
u kien hemm node mill-inqas wieħed

357
00:16:51,780 --> 00:16:57,070
diġà fis-seħħ, jekk dan huwa l-lista
hawn u I daħħal node ġdid hawn, I

358
00:16:57,070 --> 00:17:01,840
għandek bżonn tagħmel ċert li node ex tiegħi
punti lura lill node ġdid tiegħi,

359
00:17:01,840 --> 00:17:04,260
għaliex dan huwa, għal darb'oħra,
lista marbuta doppjament.

360
00:17:04,260 --> 00:17:05,460
>> Allura aħna tagħmel verifika sanità.

361
00:17:05,460 --> 00:17:10,109
Jekk il-lista ma huwiex null, jekk hemm diġà
lymph wieħed jew aktar hemmhekk, allura

362
00:17:10,109 --> 00:17:12,470
jżidu li back referenza biex ngħidu hekk.

363
00:17:12,470 --> 00:17:15,420
U allura l-ħafna aħħar ħaġa li għandna bżonn
tagħmel huwa attwalment taġġorna l-globali

364
00:17:15,420 --> 00:17:20,329
lista varjabbli ruħha għall-punt
għal dak node ġdid.

365
00:17:20,329 --> 00:17:21,790
Yeah.

366
00:17:21,790 --> 00:17:26,579
>> UDJENZA: Fil-vleġġa pointer
[Inaudible] hija ugwali null, ma li

367
00:17:26,579 --> 00:17:30,420
tittratta l-lista għaliex
il-lista huwa null?

368
00:17:30,420 --> 00:17:30,596
>> DAVID J. Malan: Nope.

369
00:17:30,596 --> 00:17:34,500
Dan huwa sempliċiment me tkun proattiv
bir-reqqa, b'mod li jekk dan huwa tiegħi

370
00:17:34,500 --> 00:17:38,730
lista oriġinali ma forsi xi lymph aktar
minn hawn u jien ddaħħal tiegħi

371
00:17:38,730 --> 00:17:42,380
node ġdid hawn, hemm għaddej
li tkun xejn hawn.

372
00:17:42,380 --> 00:17:44,720
U nixtieq li jaqbdu l-idea
billi jistabbilixxu preċedenti li

373
00:17:44,720 --> 00:17:47,740
null fuq il-node ġdid.

374
00:17:47,740 --> 00:17:51,410
U preżumibbilment, jekk il-kodiċi tiegħi hija korretta
u hemm ebda mod ieħor li daħħal

375
00:17:51,410 --> 00:17:54,970
punti strateġiċi oħrajn minn din il-funzjoni,
preżumibbilment, anki jekk il-lista diġà

376
00:17:54,970 --> 00:18:00,090
lymph wieħed jew aktar fiha, preżumibbilment l-
lista, l-ewwel node, ikollu

377
00:18:00,090 --> 00:18:02,750
pointer preċedenti ta null innifsu.

378
00:18:02,750 --> 00:18:03,550
>> UDJENZA: U biss segwitu.

379
00:18:03,550 --> 00:18:08,139
Ir-raġuni inti tpoġġi pointer ugwali jmiss
lista int tagħmel il-pointer

380
00:18:08,139 --> 00:18:13,579
qabel lista li huwa tipponta
għall-ieħor, I raden -

381
00:18:13,579 --> 00:18:14,980
I Don -

382
00:18:14,980 --> 00:18:15,450
biss jelenka?

383
00:18:15,450 --> 00:18:16,400
>> DAVID J. Malan: Eżattament.

384
00:18:16,400 --> 00:18:19,400
U hekk ejja attwalment jikkunsidraw żewġ każijiet
hawn verament, anki jekk il-

385
00:18:19,400 --> 00:18:22,070
sabiex aħna ser jikkunsidraw lilhom mhix
pjuttost l-istess bħall-kodiċi.

386
00:18:22,070 --> 00:18:26,250
Iżda fuq livell għoli, jekk din tirrapreżenta
lista u din hija 32-bit

387
00:18:26,250 --> 00:18:29,560
pointer, ix-xenarju sempliċi hija
li dan huwa null fil-kontumaċja.

388
00:18:29,560 --> 00:18:33,010
U jissoponi nixtieq li daħħal il-
numru 50 kien l-ewwel numru.

389
00:18:33,010 --> 00:18:37,640
Hekk jien ser imorru quddiem u jallokaw
node, li se jkun fiha

390
00:18:37,640 --> 00:18:38,770
tliet oqsma -

391
00:18:38,770 --> 00:18:42,070
n, qabel, u li jmiss.

392
00:18:42,070 --> 00:18:44,580
>> Jien ser tpoġġi l-għadd 50
hawn, għaliex dan se jkun n.

393
00:18:44,580 --> 00:18:46,130
Dan se jkun jmiss.

394
00:18:46,130 --> 00:18:48,530
U dan se jkun ta 'qabel.

395
00:18:48,530 --> 00:18:50,910
U hekk x'għandi nagħmel f'dan il-każ?

396
00:18:50,910 --> 00:18:53,900
Well, stajt biss isir linja 1 hawn.

397
00:18:53,900 --> 00:18:55,400
Pointer n gets n.

398
00:18:55,400 --> 00:18:57,740
Jien imbagħad qal, qabel
għandhom jingħataw null.

399
00:18:57,740 --> 00:18:59,470
Allura dan se jkun null.

400
00:18:59,470 --> 00:19:01,365
Imbagħad jien se ngħid li jmiss
hija se tikseb lista.

401
00:19:01,365 --> 00:19:05,150
>> U dan biss xogħlijiet out ukoll.

402
00:19:05,150 --> 00:19:06,500
Dan huwa null.

403
00:19:06,500 --> 00:19:10,620
U hekk jien qal, il-l-node ġdid li jmiss
qasam għandha tikseb xi din hija.

404
00:19:10,620 --> 00:19:12,570
Allura li tpoġġi null ieħor hemmhekk.

405
00:19:12,570 --> 00:19:14,510
U allura l-aħħar ħaġa
I do huwa check hawn.

406
00:19:14,510 --> 00:19:17,870
Jekk il-lista mhix ugwali għal null, iżda
hija ugwali għal null, hekk aħna skip li

407
00:19:17,870 --> 00:19:18,470
għal kollox.

408
00:19:18,470 --> 00:19:23,520
U hekk kollha I do jmiss huwa lista gets
pointer, li pictorially jirriżulta

409
00:19:23,520 --> 00:19:25,570
stampa bħal dik.

410
00:19:25,570 --> 00:19:26,620
Allura dak xenarju wieħed.

411
00:19:26,620 --> 00:19:30,490
>> U dak li inti kienu tistaqsi dwar
speċifikament hija sitwazzjoni bħal din,

412
00:19:30,490 --> 00:19:33,190
fejn diġà għandna lista one-node.

413
00:19:33,190 --> 00:19:36,240
U jekk immur lura up fl-oriġinal
dikjarazzjoni problema, il-li jmiss aħna ser

414
00:19:36,240 --> 00:19:39,320
daħħal ngħid huwa 34, biss għall-
raġunijiet ta 'diskussjoni.

415
00:19:39,320 --> 00:19:46,210
Hekk jien ser biss konvenjenti
tfassal dik hawn fuq.

416
00:19:46,210 --> 00:19:47,540
Stajt biss malloced.

417
00:19:47,540 --> 00:19:49,310
Ejja nassumu jien iċċekkjar għall null.

418
00:19:49,310 --> 00:19:51,870
>> Issa, jien ser initialize
n li jkun 34.

419
00:19:51,870 --> 00:19:53,040
U dan se jkun n.

420
00:19:53,040 --> 00:19:54,670
Dan se jkun jmiss.

421
00:19:54,670 --> 00:19:57,100
U dan se jkun ta 'qabel.

422
00:19:57,100 --> 00:19:59,370
Ejja jagħmlu ċert I ma
tikseb dan lura.

423
00:19:59,370 --> 00:20:01,110
Preċedenti jiġi l-ewwel
fid-definizzjoni.

424
00:20:01,110 --> 00:20:03,070
Let me jiffissaw dan.

425
00:20:03,070 --> 00:20:04,410
Dan huwa qabel.

426
00:20:04,410 --> 00:20:05,780
Dan huwa li jmiss.

427
00:20:05,780 --> 00:20:08,620
Anke jekk dawn huma identiċi,
ejja tinżamm konsistenti.

428
00:20:08,620 --> 00:20:09,450
>> Preċedenti.

429
00:20:09,450 --> 00:20:11,030
Dan huwa li jmiss.

430
00:20:11,030 --> 00:20:16,310
So I stajt biss malloced nota tiegħi, ikkontrollati
għall null, assenjati 34 fil-node.

431
00:20:16,310 --> 00:20:17,570
Preċedenti gets null.

432
00:20:17,570 --> 00:20:19,480
Allura li tagħti me dak.

433
00:20:19,480 --> 00:20:21,010
Next gets lista.

434
00:20:21,010 --> 00:20:22,370
Allura lista hija din.

435
00:20:22,370 --> 00:20:26,520
Allura dan huwa l-istess bħal issa tpinġija dan
vleġġa, b'tali mod li dawn jindikaw waħda

436
00:20:26,520 --> 00:20:27,940
fl-istess.

437
00:20:27,940 --> 00:20:30,400
U mbagħad jien iċċekkjar jekk lista
mhuwiex ugwali għal null.

438
00:20:30,400 --> 00:20:31,740
U m'humiex dan iż-żmien.

439
00:20:31,740 --> 00:20:35,580
Imbagħad jien ser tagħmel lista
preċedenti gets pointer.

440
00:20:35,580 --> 00:20:39,700
>> Allura lista preċedenti gets PTR.

441
00:20:39,700 --> 00:20:44,300
Allura dan għandu l-effett li tpoġġi
vleġġa grafika hawn.

442
00:20:44,300 --> 00:20:46,930
U li jkollna ftit
immewġin, il-linji.

443
00:20:46,930 --> 00:20:50,780
U mbagħad, fl-aħħarnett, I taġġorna
lista għall-punt li pointer.

444
00:20:50,780 --> 00:20:55,560
Hekk issa dan jindika li dan Guy.

445
00:20:55,560 --> 00:20:57,170
U issa, ejja do a quick
check sanità.

446
00:20:57,170 --> 00:20:59,470
>> Hawn il-lista, li hija
il-varjabbli globali.

447
00:20:59,470 --> 00:21:02,850
L-ewwel node huwa, tabilħaqq, 34, minħabba
Jien wara dik vleġġa.

448
00:21:02,850 --> 00:21:05,210
U li korretta għaliex nixtieq li
daħħal fil-bidu tal-lista

449
00:21:05,210 --> 00:21:06,070
kollha lymph ġodda.

450
00:21:06,070 --> 00:21:08,860
Qasam li jmiss tiegħu twassalni għal dan Guy.

451
00:21:08,860 --> 00:21:10,710
Jekk I iżommu għaddejjin, I hit li jmiss huwa null.

452
00:21:10,710 --> 00:21:11,760
Hekk hemm ebda lista aktar.

453
00:21:11,760 --> 00:21:14,460
Jekk I hit preċedenti, nasal
lura fejn I jistennew.

454
00:21:14,460 --> 00:21:16,435
>> Allura għad hemm ftit indikaturi,
ovvjament, li jimmanipulaw.

455
00:21:16,435 --> 00:21:19,870
Imma l-fatt li inti qalulhom li tagħmel
din fil-ħin kostanti ifisser li inti biss

456
00:21:19,870 --> 00:21:22,910
għandhom numru finit ta 'affarijiet
int permess li tagħmel.

457
00:21:22,910 --> 00:21:24,290
U dak li huwa dak in-numru?

458
00:21:24,290 --> 00:21:25,185
Jista 'jkun pass wieħed.

459
00:21:25,185 --> 00:21:25,700
Jista 'jkun tnejn.

460
00:21:25,700 --> 00:21:26,820
Jista 'jkun 1,000 passi.

461
00:21:26,820 --> 00:21:30,500
Iżda huwa finite, li jfisser li inti ma tistax
kwalunkwe tip ta 'looping għaddej

462
00:21:30,500 --> 00:21:32,010
hawn, l-ebda recursion, ebda loops.

463
00:21:32,010 --> 00:21:37,390
Huwa biss ltqajna biex ikunu linji hard-kodifikati
ta 'kodiċi kif għandna f'dan kampjun.

464
00:21:37,390 --> 00:21:42,330
>> Allura l-problema li jmiss 12 talabna biex
tlesti l-implimentazzjoni tal neħħi

465
00:21:42,330 --> 00:21:46,740
taħt b'tali mod li tneħħi
n mil-lista fil-ħin lineari.

466
00:21:46,740 --> 00:21:48,740
Hekk ikollok ftit aktar
kamra wiggle issa.

467
00:21:48,740 --> 00:21:52,380
Inti jista 'jassumi li n, jekk preżenti
fil-lista, se jkunu preżenti

468
00:21:52,380 --> 00:21:53,340
mhux aktar minn darba.

469
00:21:53,340 --> 00:21:56,770
U li wisq huwa intenzjonat li jkun ibbażat fuq il-kwizz
simplifikazzjoni suppożizzjoni, hekk

470
00:21:56,770 --> 00:21:59,780
li jekk issib in-numru 50 x'imkien
fil-lista, inti ma wkoll

471
00:21:59,780 --> 00:22:02,890
jkollhom għalfejn tinkwieta dwar tkompli
jtenni, tfittex kull possibbli

472
00:22:02,890 --> 00:22:06,990
kopja ta '50, li kien biss jiddevolvu
fis xi dettall fil-ħin limitat.

473
00:22:06,990 --> 00:22:10,460
>> Allura ma tneħħi, dan wieħed kien definittivament
aktar ta 'sfida u aktar

474
00:22:10,460 --> 00:22:11,640
kodiċi li tikteb.

475
00:22:11,640 --> 00:22:14,990
Iżda fl-ewwel daqqa t'għajn, franchement, huwa jista '
tfittex xi ħaġa kbira u simili

476
00:22:14,990 --> 00:22:17,060
hemm ebda mod inti jista 'jkollhom
toħroġ bi fuq kwizz.

477
00:22:17,060 --> 00:22:22,450
Imma jekk aħna niffukaw fuq il-passi individwali,
wieħed jittama, se f'daqqa

478
00:22:22,450 --> 00:22:26,060
jolqot lilek li kull wieħed minn dawn individwali
passi jagħmel sens ovvju

479
00:22:26,060 --> 00:22:27,080
retrospettivament.

480
00:22:27,080 --> 00:22:28,200
Mela ejja tagħti ħarsa.

481
00:22:28,200 --> 00:22:32,570
>> Allura l-ewwel, aħna initialize pointer
li tkun lista innifsu.

482
00:22:32,570 --> 00:22:36,040
Għaliex nixtieq ħin lineari, li l-mezzi
Jien ser ikollhom xi loop.

483
00:22:36,040 --> 00:22:39,730
U mod komuni biex jtenni fuq il-
nodes fi struttura lista jew kwalunkwe tip

484
00:22:39,730 --> 00:22:43,860
ta 'struttura iteratively huwa li jieħdu
pointer lejn il-quddiem tad-data

485
00:22:43,860 --> 00:22:46,990
istruttura u mbagħad biss tibda aġġornament
dan u jimxu tiegħek mod

486
00:22:46,990 --> 00:22:48,650
permezz tal-istruttura tad-data.

487
00:22:48,650 --> 00:22:50,040
Hekk jien ser tagħmel eżattament dan.

488
00:22:50,040 --> 00:22:54,260
>> Filwaqt pointer, varjabbli temporanju tiegħi,
mhuwiex ugwali għal null, ejja

489
00:22:54,260 --> 00:22:55,660
imorru quddiem u jiċċekkjaw.

490
00:22:55,660 --> 00:22:56,910
Did I nikseb xxurtjati?

491
00:22:56,910 --> 00:23:01,740
Huwa l-qasam n fil-node jien bħalissa
tħares lejn ugwali għall-

492
00:23:01,740 --> 00:23:03,380
Numru jien infittxu?

493
00:23:03,380 --> 00:23:05,410
U jekk iva, ejja nagħmlu xi ħaġa.

494
00:23:05,410 --> 00:23:10,020
Issa, avviż dan jekk il-kundizzjoni
jdawru l kollu

495
00:23:10,020 --> 00:23:11,520
ġejjin linji ta 'kodiċi.

496
00:23:11,520 --> 00:23:14,610
Dan huwa l-unika ħaġa I jimpurtahom -
sejba ta 'numru in kwistjoni.

497
00:23:14,610 --> 00:23:18,010
Allura hemm ebda inkella, li jissimplifika
affarijiet kunċettwali ftit.

498
00:23:18,010 --> 00:23:22,040
>> Imma issa, I realizzati, u inti jista 'jkollok
biss realizzati dan wara ħsieb

499
00:23:22,040 --> 00:23:24,720
permezz daqsxejn, hemm
attwalment żewġ każijiet hawn.

500
00:23:24,720 --> 00:23:28,060
Wieħed huwa fejn il-node huwa fil-
bidu tal-lista, li hija

501
00:23:28,060 --> 00:23:31,040
ftit annoying, għaliex thats
każ speċjali, għax għandek biex jittrattaw

502
00:23:31,040 --> 00:23:33,340
ma 'dan il-ħaġa, li
huwa l-uniku anomalija.

503
00:23:33,340 --> 00:23:35,720
Kullimkien inkella fil-lista,
huwa l-istess ħaġa.

504
00:23:35,720 --> 00:23:38,050
Hemm node preċedenti u li jmiss
node, node preċedenti, node jmiss.

505
00:23:38,050 --> 00:23:40,940
Iżda dan Guy huwa ftit speċjali
jekk hu fil-bidu.

506
00:23:40,940 --> 00:23:48,710
>> Allura jekk il-pointer huwa daqs il-lista
nnifisha, hekk jekk jien fil-bidu ta '

507
00:23:48,710 --> 00:23:53,960
il-lista u I sabu n, I bżonn
biex jagħmlu ftit affarijiet.

508
00:23:53,960 --> 00:23:59,230
Waħda, I bżonn għall-bidla lista biex
punt għall-qasam li jmiss, 50.

509
00:23:59,230 --> 00:24:01,270
So jissoponi li jien jippruvaw
biex jitneħħew 34.

510
00:24:01,270 --> 00:24:03,560
Allura li dan Guy ltqajna biex tmur
bogħod fi ftit mument.

511
00:24:03,560 --> 00:24:07,210
>> Hekk jien se ngħid, lista
gets pointer li jmiss.

512
00:24:07,210 --> 00:24:08,570
Ukoll, dan huwa pointer.

513
00:24:08,570 --> 00:24:10,360
Li jmiss hija li tipponta hawn fuq.

514
00:24:10,360 --> 00:24:17,470
Allura dan qed tinbidel dan id-dritt arrow
issa għall-punt li dan Guy hawn.

515
00:24:17,470 --> 00:24:19,580
Issa, ftakar, għandna
varjabbli temporanja.

516
00:24:19,580 --> 00:24:23,520
Allura aħna ma orfni xi nodes,
minħabba I wkoll ikollhom dan Guy fil tiegħi

517
00:24:23,520 --> 00:24:25,010
implimentazzjoni tal tneħħi.

518
00:24:25,010 --> 00:24:29,600
Allura issa, jekk il-lista nnifisha mhix null,
I ħtieġa li jiffissaw ftit xi ħaġa.

519
00:24:29,600 --> 00:24:32,690
>> I bżonn issa tiżgura li dan vleġġa,
li qabel kienu tipponta

520
00:24:32,690 --> 00:24:36,830
50-34, dan s'est li jmorru lil hinn,
għaliex jekk jien tipprova teħles

521
00:24:36,830 --> 00:24:41,910
ta '34, 50 kienu aħjar ma jżomm kwalunkwe
tip ta 'back referenza għalih bħala l-

522
00:24:41,910 --> 00:24:42,820
vleġġa suġġerit.

523
00:24:42,820 --> 00:24:44,820
So I biss ma din il-linja.

524
00:24:44,820 --> 00:24:46,520
Mela allura jien jsir.

525
00:24:46,520 --> 00:24:48,040
F'dak il-każ huwa attwalment pjuttost faċli.

526
00:24:48,040 --> 00:24:51,010
Tqattiegħ off-kap tal-lista
huwa relattivament sempliċi.

527
00:24:51,010 --> 00:24:52,980
>> Sfortunatament, hemm dan
blokk annoying ieħor.

528
00:24:52,980 --> 00:24:56,170
Allura issa, I għandek tikkunsidra l-każ
fejn hemm xi ħaġa fin-nofs.

529
00:24:56,170 --> 00:24:59,880
Iżda mhux wisq terribbli, ħlief
għal sintassi bħal dan.

530
00:24:59,880 --> 00:25:03,080
Mela jekk jien ma fil-bidu tal-
lista, jien x'imkien fin-nofs.

531
00:25:03,080 --> 00:25:08,160
U din il-linja hawnhekk qed tgħid, bidu
fi kwalunkwe node int fuq.

532
00:25:08,160 --> 00:25:11,210

533
00:25:11,210 --> 00:25:18,550
Mur fil-qasam li jmiss tal-node qabel
u l-punt li fil-pointer.

534
00:25:18,550 --> 00:25:20,390
>> Ejja nagħmlu dan pictorially.

535
00:25:20,390 --> 00:25:21,640
Li kien qed ikkumplikata.

536
00:25:21,640 --> 00:25:30,480

537
00:25:30,480 --> 00:25:37,990
Mela jekk għandi oqsma preċedenti hawn -
ejja tagħmel dan - oqsma li jmiss hawn.

538
00:25:37,990 --> 00:25:41,200
Jien ser tissimplifika pointers tiegħi pjuttost
minn jiġbed mazz sħiħ ta '

539
00:25:41,200 --> 00:25:45,710
affarijiet quddiem u lura crisscrossing
xulxin.

540
00:25:45,710 --> 00:25:50,870
U issa, ejja biss jgħidu li dan huwa 1, 2,
3 għall-fini ta 'diskussjoni, anke

541
00:25:50,870 --> 00:25:53,410
għalkemm dan ma line up ma '
il-problema inkwistjoni.

542
00:25:53,410 --> 00:25:55,900
>> Allura hawnhekk lista marbuta tiegħi.

543
00:25:55,900 --> 00:25:59,300
I am tipprova tneħħi tnejn f'din
verżjoni partikolari ta 'l-istorja.

544
00:25:59,300 --> 00:26:01,960
Hekk stajt aġġornati pointer biex
tkun tipponta lejn dan Guy.

545
00:26:01,960 --> 00:26:03,315
Allura dan huwa PTR.

546
00:26:03,315 --> 00:26:04,530
Hu tipponta hawn.

547
00:26:04,530 --> 00:26:07,170
Din hija lista, li teżisti
globalment bħal qabel.

548
00:26:07,170 --> 00:26:09,200
U hu tipponta hawn x'ikun.

549
00:26:09,200 --> 00:26:10,800
U issa, jien tipprova tneħħi tnejn.

550
00:26:10,800 --> 00:26:13,850
>> Mela jekk pointer hija li tipponta hawn, jien
ser isegwu, apparentement, il-

551
00:26:13,850 --> 00:26:17,110
pointer preċedenti, li jpoġġi lili fl-1.

552
00:26:17,110 --> 00:26:22,290
Jien imbagħad se ngħid li jmiss
qasam, li jwassalni fuq għal dan

553
00:26:22,290 --> 00:26:25,410
kaxxa hawn, se
pointer ugwali jmiss.

554
00:26:25,410 --> 00:26:28,400
Hekk jekk dan il-werrej, dan huwa li jmiss.

555
00:26:28,400 --> 00:26:31,840
Dan ifisser li dan vleġġa bżonnijiet
għall-punt li dan Guy.

556
00:26:31,840 --> 00:26:35,140
>> Allura dak li l-linja tal-kodiċi għandu biss
jsir huwa xi ftit ta 'dan.

557
00:26:35,140 --> 00:26:37,500
U issa, dan huwa tfittex bħal
pass fid-direzzjoni t-tajba.

558
00:26:37,500 --> 00:26:41,390
Aħna essenzjalment tixtieq snip 2 out
tal-nofs ta '1 u 3.

559
00:26:41,390 --> 00:26:44,400
Għalhekk jagħmel sens li rridu
rotta din pointer madwaru.

560
00:26:44,400 --> 00:26:50,400
Allura din il-linja li jmiss qed jiċċekkja jekk pointer
jmiss ma huwiex null, hemm

561
00:26:50,400 --> 00:26:54,200
tabilħaqq xi ħadd li d-dritt ta '2,
li jfisser irridu wkoll tagħmel

562
00:26:54,200 --> 00:26:55,850
ftit snip hawn.

563
00:26:55,850 --> 00:27:00,590
>> So I issa jeħtieġ li jsegwu dan il-werrej
u taġġorna l-pointer preċedenti dwar

564
00:27:00,590 --> 00:27:05,410
dan Guy li tagħmel ftit ta '
workaround hawn il-punt hawnhekk.

565
00:27:05,410 --> 00:27:07,100
U issa, viżwalment dan huwa sbieħ.

566
00:27:07,100 --> 00:27:11,930
Huwa ftit messy f'dak hemm
ebda waħda tipponta lejn l-2 aktar.

567
00:27:11,930 --> 00:27:13,600
2 hija li tipponta lejn ix-xellug.

568
00:27:13,600 --> 00:27:14,980
U 2 hija li tipponta lejn il-lemin.

569
00:27:14,980 --> 00:27:17,480
Imma hu jista 'jagħmel kull ma trid, għax
hu wasal biex tikseb meħlusa.

570
00:27:17,480 --> 00:27:19,480
U ma jimpurtax liema
dawk il-valuri huma aktar.

571
00:27:19,480 --> 00:27:23,040
>> X'hemm importanti huwa li l-bqija
guys huma routing hawn fuq

572
00:27:23,040 --> 00:27:24,280
u taħt lilu issa.

573
00:27:24,280 --> 00:27:25,810
U fil-fatt, dan huwa dak li nagħmlu jmiss.

574
00:27:25,810 --> 00:27:29,360
Aħna pointer ħielsa, li jfisser li għandna tgħid il-
sistema operattiva, inti merħba

575
00:27:29,360 --> 00:27:30,906
li titlob lura dan.

576
00:27:30,906 --> 00:27:34,900
U mbagħad fl-aħħar, nerġgħu lura.

577
00:27:34,900 --> 00:27:37,220
Else impliċitament, jekk aħna
ma ġewx lura s'issa,

578
00:27:37,220 --> 00:27:38,290
konna ltqajna biex iżommu tfittex.

579
00:27:38,290 --> 00:27:41,485
Allura pointer ugwali pointer li jmiss biss
ifisser jimxu dan Guy hawn.

580
00:27:41,485 --> 00:27:42,600
Nimxu dan Guy hawn.

581
00:27:42,600 --> 00:27:45,400
Nimxu dan Guy hawn jekk, fil-fatt,
aħna ma sabx l-għadd

582
00:27:45,400 --> 00:27:46,960
aħna qed tfittex għal darb'oħra.

583
00:27:46,960 --> 00:27:49,630
>> Allura franchement, jidher kompletament
kbira, I think, fl-ewwel

584
00:27:49,630 --> 00:27:52,180
daqqa t'għajn, speċjalment jekk inti tħabtu
ma 'dan matul l-kwizz mbagħad tara

585
00:27:52,180 --> 00:27:52,850
xi ħaġa bħal din.

586
00:27:52,850 --> 00:27:55,050
U inti pat lilek innifsek fuq id-dahar.

587
00:27:55,050 --> 00:27:57,080
Ukoll, hemm ebda mod I jista 'jkollhom
toħroġ ma 'dak fuq il-kwizz.

588
00:27:57,080 --> 00:28:00,470
Iżda nixtieq jargumentaw, inti tista 'jekk inti break
isfel lejn dawn individwali

589
00:28:00,470 --> 00:28:04,400
każijiet u biss walk permezz ta 'dan
bir-reqqa, għalkemm, ċertament, taħt

590
00:28:04,400 --> 00:28:06,300
ċirkostanzi stressanti.

591
00:28:06,300 --> 00:28:09,470
>> Thankfully, l-istampa magħmula
kollox kuntenti.

592
00:28:09,470 --> 00:28:11,050
Inti tista 'tiġbed dan
kwalunkwe numru ta 'modi.

593
00:28:11,050 --> 00:28:12,760
Inti ma għandekx tagħmel l crisscrossing
ħaġa hawn.

594
00:28:12,760 --> 00:28:14,520
Inti tista 'tagħmel dan ma dritta
linji bħal dan.

595
00:28:14,520 --> 00:28:18,790
Iżda l-gist ta 'din il-problema, fil-
ġenerali, kien li tirrealizza li l-

596
00:28:18,790 --> 00:28:22,060
stampa fl-aħħar għandha tfittex ftit
xi ħaġa bħal din, minħabba li

597
00:28:22,060 --> 00:28:25,030
ħin kostanti implika li inti żżomm
disturbazzjoni u disturbazzjoni u disturbazzjoni l-

598
00:28:25,030 --> 00:28:29,900
punti strateġiċi ġodda fil-bidu
tal-lista.

599
00:28:29,900 --> 00:28:31,960
Kwalunkwe mistoqsijiet?

600
00:28:31,960 --> 00:28:34,565
Probabbilment l-aktar sfida ta '
ċertament l-mistoqsijiet kodifikazzjoni.

601
00:28:34,565 --> 00:28:37,690
>> UDJENZA: Allura huwa lista simili għal
ras eżempji preċedenti.

602
00:28:37,690 --> 00:28:39,640
>> DAVID J. Malan: Eżattament, eżattament.

603
00:28:39,640 --> 00:28:43,130
Just isem differenti għall-
varjabbli globali.

604
00:28:43,130 --> 00:28:44,380
Madwar id-dinja liema?

605
00:28:44,380 --> 00:28:48,880

606
00:28:48,880 --> 00:28:49,730
>> ROB BOWDEN: OK.

607
00:28:49,730 --> 00:28:52,020
Allura dan huwa dak fejn inti
kellu jikteb il-paragrafu.

608
00:28:52,020 --> 00:28:56,060
Xi nies kiteb esejs
għal din il-mistoqsija.

609
00:28:56,060 --> 00:29:00,230
Imma inti biss bżonn jużaw dawn is-sitt termini
biex jiddeskrivu dak li jiġri meta

610
00:29:00,230 --> 00:29:02,440
inti tipprova tikkuntattja facebook.com.

611
00:29:02,440 --> 00:29:07,930
So I ser biss jitkellmu permezz tal-proċess
jużaw dawn it-termini kollha.

612
00:29:07,930 --> 00:29:11,290
Allura fil-browser tagħna, aħna tip facebook.com
u hit Ikteb.

613
00:29:11,290 --> 00:29:17,280
Allura browser tagħna għaddej biex jinbena
HTTP titlob li għaddej biex tibgħat

614
00:29:17,280 --> 00:29:22,220
permezz ta 'xi proċess biex Facebook għal
Facebook biex jirrispondu lilna mal-

615
00:29:22,220 --> 00:29:24,450
HTML tal-paġna tagħha.

616
00:29:24,450 --> 00:29:28,800
>> Allura dak li huwa l-proċess
li t-talba HTTP

617
00:29:28,800 --> 00:29:30,730
attwalment gets Facebook?

618
00:29:30,730 --> 00:29:32,790
Allura l-ewwel, għandna bżonn biex tittraduċi
Facebook.com.

619
00:29:32,790 --> 00:29:38,780
Hekk biss minħabba l-isem Facebook.com,
fejn attwalment ma t-talba HTTP

620
00:29:38,780 --> 00:29:39,940
bżonn biex tmur?

621
00:29:39,940 --> 00:29:44,120
Għalhekk għandna bżonn li jittraduċu Facebook.com
għal indirizz IP, li unikament

622
00:29:44,120 --> 00:29:47,620
jidentifika liema magna għandna attwalment
trid tibgħat din it-talba.

623
00:29:47,620 --> 00:29:49,310
Laptop tiegħek ikollu indirizz IP.

624
00:29:49,310 --> 00:29:52,240
Xejn konness mal-internet
għandha l-indirizz IP.

625
00:29:52,240 --> 00:29:59,030
>> Allura DNS, Domain Name System, li hija
dak li għaddej biex jimmaniġġaw it-traduzzjoni

626
00:29:59,030 --> 00:30:03,750
minn facebook.com għal indirizz IP li
inti fil-fatt tixtieq tikkuntattja.

627
00:30:03,750 --> 00:30:08,075
Allura aħna tikkuntattja l-DNS servers u
jiġifieri, dak li huwa facebook.com?

628
00:30:08,075 --> 00:30:16,560
Huwa jgħid, oh, huwa IP indirizz 190.212
xi ħaġa, xi ħaġa, xi ħaġa.

629
00:30:16,560 --> 00:30:16,900
Kull dritt.

630
00:30:16,900 --> 00:30:18,850
Issa, naf liema magna
I tixtieq tikkuntattja.

631
00:30:18,850 --> 00:30:22,360
>> Mela allura inti tibgħat talba HTTP tiegħek
lejn dik magna.

632
00:30:22,360 --> 00:30:24,140
Allura kif ma jiksbu għal dak magna?

633
00:30:24,140 --> 00:30:27,200
Ukoll, it-talba jmur minn
router li bouncing router.

634
00:30:27,200 --> 00:30:32,630
Ftakar l-eżempju fil-klassi, fejn
għandna attwalment raw ir-rotta li l-

635
00:30:32,630 --> 00:30:35,340
pakketti ħa meta aħna ppruvaw
biex jikkomunikaw.

636
00:30:35,340 --> 00:30:38,460
Rajna dan jaqbżu fuq l-Atlantiku
Oċean fuq punt wieħed jew ikun x'ikun.

637
00:30:38,460 --> 00:30:42,820
>> Allura l-aħħar port tul.

638
00:30:42,820 --> 00:30:46,520
Allura issa dan huwa fuq il-kompjuter tiegħek.

639
00:30:46,520 --> 00:30:49,970
Inti jista 'jkollhom affarijiet multipli bħalissa
komunikazzjoni mal-internet.

640
00:30:49,970 --> 00:30:53,730
So I tista 'tkun qed taħdem, jiġifieri, Skype.

641
00:30:53,730 --> 00:30:55,670
I jista 'jkollhom web browser miftuħa.

642
00:30:55,670 --> 00:30:59,010
I jista 'jkollhom xi ħaġa li
torrenting files.

643
00:30:59,010 --> 00:31:00,880
Allura kollha ta 'dawn l-affarijiet huma
komunikazzjoni mal-

644
00:31:00,880 --> 00:31:02,600
internet b'xi mod.

645
00:31:02,600 --> 00:31:08,070
>> Allura meta l-kompjuter tiegħek tirċievi xi data
mill-internet, kif ma dan

646
00:31:08,070 --> 00:31:10,130
taf liema applikazzjoni attwalment
irid li l-data?

647
00:31:10,130 --> 00:31:12,610
Kif tkun taf jekk din partikolari
data huwa maħsub għall-

648
00:31:12,610 --> 00:31:16,070
torrenting applikazzjoni għall-kuntrarju
għall-web browser?

649
00:31:16,070 --> 00:31:20,980
Allura dan huwa l-iskop tal-portijiet f'dak
dawn l-applikazzjonijiet jkollhom

650
00:31:20,980 --> 00:31:22,720
ddikjaraw port fuq il-kompjuter tiegħek.

651
00:31:22,720 --> 00:31:27,580
Allura web browser tiegħek jgħid, ħej,
Qiegħda nisma fuq il-port 1000.

652
00:31:27,580 --> 00:31:32,240
U l-programm torrenting tiegħek huwa qal,
Qiegħda nisma fuq il-port 3000.

653
00:31:32,240 --> 00:31:34,770
U Skype jgħid, jien jużaw port 4000.

654
00:31:34,770 --> 00:31:41,950
>> Allura meta ikollok xi data li tappartjeni
għal waħda minn dawn l-applikazzjonijiet, id-data

655
00:31:41,950 --> 00:31:45,510
huwa mmarkat li magħhom port attwalment
għandhom jintbagħtu flimkien biex.

656
00:31:45,510 --> 00:31:47,950
Allura dan jgħid, oh, I jappartjenu
port 1000.

657
00:31:47,950 --> 00:31:50,950
Naf imbagħad I bżonn biex jgħaddi din
flimkien biex web browser tiegħi.

658
00:31:50,950 --> 00:31:56,440
Allura r-raġuni huwa rilevanti hawnhekk
hija li servers mill-web tendenza li

659
00:31:56,440 --> 00:31:58,240
jisimgħu fuq il-port 80.

660
00:31:58,240 --> 00:32:02,420
Allura meta I tikkuntattja Facebook.com, jien
komunikazzjoni ma 'xi magna.

661
00:32:02,420 --> 00:32:06,390
Imma I bżonn biex ngħid li port ta 'dak
magna Irrid li jikkomunikaw ma.

662
00:32:06,390 --> 00:32:09,160
U servers mill-web tendenza li jkunu
jisimgħu fuq il-port 80.

663
00:32:09,160 --> 00:32:14,010
>> Jekk riedu, dawn jistgħu jistabbilixxu li
up hekk hija telenka fuq port 7000.

664
00:32:14,010 --> 00:32:19,090
U mbagħad fil-web browser, I tista '
manwalment tip Facebook.com: 7000 sa

665
00:32:19,090 --> 00:32:24,600
tibgħat it-talba lill-port 7000
ta 'web server Facebook.

666
00:32:24,600 --> 00:32:26,820
>> DAVID J. Malan: U f'dan il-każ, anki
għalkemm aħna ma jeħtieġu li n-nies

667
00:32:26,820 --> 00:32:30,000
jsemmi dan, f'dan il-każ, liema port
kieku t-talba fil-fatt imorru għall?

668
00:32:30,000 --> 00:32:36,630

669
00:32:36,630 --> 00:32:37,880
Erġa 'pprova.

670
00:32:37,880 --> 00:32:42,810

671
00:32:42,810 --> 00:32:44,300
Eżattament.

672
00:32:44,300 --> 00:32:47,960
Ma tfittex għal dan, iżda subtlety
li hemm xejn l-aħħar.

673
00:32:47,960 --> 00:32:51,770
>> ROB BOWDEN: Allura l-HTTPS, peress li huwa
jisimgħu speċifikament għall-

674
00:32:51,770 --> 00:32:55,180
encrypted, huwa fuq il-port 4430.

675
00:32:55,180 --> 00:32:57,680
>> Udjenza: U emails huma 25, id-dritt?

676
00:32:57,680 --> 00:33:00,670
>> DAVID J. Malan: Outbound
emails, 25, Yep.

677
00:33:00,670 --> 00:33:03,760
>> ROB BOWDEN: I lanqas biss jafu aktar ta '
il - kollha ta 'dawk aktar baxxi għandhom tendenza li jkunu

678
00:33:03,760 --> 00:33:06,310
riżervati għall-affarijiet.

679
00:33:06,310 --> 00:33:09,260
I think kollox taħt
1024 hija rriżervata.

680
00:33:09,260 --> 00:33:13,450
>> UDJENZA: Għaliex ma inti tgħid
3 kien in-numru ħażin?

681
00:33:13,450 --> 00:33:18,820
>> ROB BOWDEN: Minħabba fl-indirizz IP,
hemm erba 'gruppi ta' numri.

682
00:33:18,820 --> 00:33:21,090
U dawn qed 0-255.

683
00:33:21,090 --> 00:33:28,060
Allura 192.168.2.1 huwa komuni
netwerk lokali indirizz IP.

684
00:33:28,060 --> 00:33:30,840
Avviż kollha ta 'dawn huma inqas minn 255.

685
00:33:30,840 --> 00:33:33,570
Allura meta I bdew mal 300, li
ma jista 'possibbilment ikollu

686
00:33:33,570 --> 00:33:35,210
kien wieħed mill-numri.

687
00:33:35,210 --> 00:33:38,170
>> DAVID J. Malan: Imma dak clip iblah
minn - ma kien CSI, fejn huma kellhom

688
00:33:38,170 --> 00:33:39,970
numru li kienet kbira wisq
għall-indirizz IP.

689
00:33:39,970 --> 00:33:42,940

690
00:33:42,940 --> 00:33:46,110
>> ROB BOWDEN: Kwalunkwe mistoqsijiet dwar dan?

691
00:33:46,110 --> 00:33:51,710
Il-wieħed li jmiss, bidla tant komplet fl
suġġett, iżda aħna għandna dan array PHP għal

692
00:33:51,710 --> 00:33:53,270
l-djar fil-quad.

693
00:33:53,270 --> 00:33:56,360
U aħna għandna lista unordered.

694
00:33:56,360 --> 00:33:59,550
U rridu li jistampa kull oġġett lista
biss li jkun fih l-isem house.

695
00:33:59,550 --> 00:34:09,090

696
00:34:09,090 --> 00:34:11,870
Allura aħna għandna loop foreach.

697
00:34:11,870 --> 00:34:17,540
Mela ftakar, s-sintassi hija foreach
array bħala punt fl-array.

698
00:34:17,540 --> 00:34:22,360
Allura permezz ta 'kull iterazzjoni tal-linja,
house se jieħu fuq waħda mill-

699
00:34:22,360 --> 00:34:24,060
Valuri ġewwa tal-firxa.

700
00:34:24,060 --> 00:34:26,530
>> Fuq l-ewwel iterazzjoni, house
se jkun Cabot House.

701
00:34:26,530 --> 00:34:30,370
Fuq iterazzjoni tieni, house se
jkun Courier House u l-bqija.

702
00:34:30,370 --> 00:34:34,370
Allura għal kull quad bħala house, aħna qed
biss jmorru għall-istampar -

703
00:34:34,370 --> 00:34:37,250
inti ukoll setgħet ittennew -

704
00:34:37,250 --> 00:34:42,199
l-oġġett lista u mbagħad isem l-dar tal-
u mbagħad agħlaq il-partita lista.

705
00:34:42,199 --> 00:34:45,210
Il-braces kaboċċi huma fakultattivi hawn.

706
00:34:45,210 --> 00:34:49,480
>> U allura aħna qal ukoll fil-kwistjoni
innifsu, ftakar li tagħlaq il-

707
00:34:49,480 --> 00:34:50,770
tag lista unordered.

708
00:34:50,770 --> 00:34:53,949
Għalhekk għandna bżonn li ħruġ modalità PHP
sabiex jagħmlu dan.

709
00:34:53,949 --> 00:35:00,280
Jew jista 'jkollna ittennew l-
qrib lista tag unordered.

710
00:35:00,280 --> 00:35:02,380
>> DAVID J. Malan: Ukoll multa hawn kieku
kienu jużaw iskola antika għal

711
00:35:02,380 --> 00:35:07,340
loop bi $ i = 0 0 u jużaw għadd sa
insemmu l-tul tal-ray.

712
00:35:07,340 --> 00:35:09,240
Totally multa wisq, just
a wordier ftit.

713
00:35:09,240 --> 00:35:12,170

714
00:35:12,170 --> 00:35:14,742
>> UDJENZA: Mela jekk inti kienu se
[Inaudible], would you do -

715
00:35:14,742 --> 00:35:16,734
I tinsa dak l loop [inaudible] hija.

716
00:35:16,734 --> 00:35:21,380
Would you $ quad i bracket?

717
00:35:21,380 --> 00:35:21,850
>> DAVID J. Malan: Eżattament.

718
00:35:21,850 --> 00:35:23,100
Yeah, eżattament.

719
00:35:23,100 --> 00:35:26,650

720
00:35:26,650 --> 00:35:27,900
>> ROB BOWDEN: Xi ħaġa oħra?

721
00:35:27,900 --> 00:35:31,350

722
00:35:31,350 --> 00:35:32,010
>> DAVID J. Malan: Kull dritt.

723
00:35:32,010 --> 00:35:32,300
Kompromessi.

724
00:35:32,300 --> 00:35:38,290
Allura kien hemm għenieqed ta 'tweġibiet
possibbli għal kull wieħed minn dawn.

725
00:35:38,290 --> 00:35:40,510
Konna verament tfittex biss għal
xi ħaġa konvinċenti għal rasu u

726
00:35:40,510 --> 00:35:41,100
żvantaġġ.

727
00:35:41,100 --> 00:35:44,830
U n-numru 16 talab, validazzjoni utenti "
input client-side, kif ma 'JavaScript,

728
00:35:44,830 --> 00:35:47,280
minflok server-ġenb, kif ma PHP.

729
00:35:47,280 --> 00:35:49,450
Allura x'hemm rasu ta '
tagħmel-naħa tal-klijent?

730
00:35:49,450 --> 00:35:53,780
>> Well, waħda mill-affarijiet aħna proposti huwa
li inti tnaqqas latency, għaliex inti

731
00:35:53,780 --> 00:35:56,750
ma għandekx li jolqot tikkuntattja lill-
server, li tista 'tieħu ftit

732
00:35:56,750 --> 00:36:00,390
millisekondi jew saħansitra ftit sekondi
billi tevita dan u biss

733
00:36:00,390 --> 00:36:04,670
validazzjoni utenti input client-side minn
tqajjem fuq jissottomettuh handler u

734
00:36:04,670 --> 00:36:06,650
biss verifika, ma dawn it-tip
xi ħaġa għall-isem?

735
00:36:06,650 --> 00:36:08,080
Did xi ħaġa tip
fl għal indirizz email?

736
00:36:08,080 --> 00:36:10,950
Ma huma jagħżlu dorm minn
il-menu drop-down?

737
00:36:10,950 --> 00:36:14,360
>> Inti tista 'tagħtihom feedback istantanja
tuża l-kompjuter gigahertz

738
00:36:14,360 --> 00:36:16,770
jew kwalunkwe ikollhom thats
attwalment fuq desk tagħhom.

739
00:36:16,770 --> 00:36:19,310
Allura huwa biss aħjar għall-utent
esperjenza tipikament.

740
00:36:19,310 --> 00:36:24,460
Iżda żvantaġġ jagħmlu client-side
validazzjoni, jekk inti tagħmel dan mingħajr wkoll

741
00:36:24,460 --> 00:36:29,860
tagħmel validazzjoni server-side hija li
xi ħadd aktar li joħorġu ta 'CS50 jaf

742
00:36:29,860 --> 00:36:33,980
li inti tista 'biss tibgħat kwalunkwe informazzjoni li inti tixtieq
għal server kwalunkwe numru ta 'modi.

743
00:36:33,980 --> 00:36:37,030
Franchement, fil-maġġoranza f'kull browser, inti tista '
ikklikkja madwar fil-settings u biss

744
00:36:37,030 --> 00:36:40,110
itfi JavaScript, li,
Għalhekk, jiskonnettja xi forma ta '

745
00:36:40,110 --> 00:36:41,080
validazzjoni.

746
00:36:41,080 --> 00:36:44,460
>> Imma int wkoll tista 'recall li anke I
għamilt xi affarijiet arcane fil-klassi bl-użu

747
00:36:44,460 --> 00:36:47,790
telnet u fil-fatt feint
tkun browser billi tibgħat get

748
00:36:47,790 --> 00:36:49,240
talbiet għal server.

749
00:36:49,240 --> 00:36:51,030
U li ċertament mhux
tuża kwalunkwe JavaScript.

750
00:36:51,030 --> 00:36:53,290
Li jinsab biss lili ittajpjar jikkmanda
fil-keyboard.

751
00:36:53,290 --> 00:36:57,410
Allura verament, kull programmer fi biżżejjed
kumdità mal-web u HTTP

752
00:36:57,410 --> 00:37:01,690
tista 'tibgħat kwalunkwe data hu jew hi trid
għal server mingħajr validazzjoni.

753
00:37:01,690 --> 00:37:05,470
U jekk server tiegħek ma tkunx ukoll verifika,
ma jagħtu me isem, huwa

754
00:37:05,470 --> 00:37:08,930
dan l-indirizz email attwalment validu, għamlet
jagħżlu dorm, inti tista 'tispiċċa

755
00:37:08,930 --> 00:37:12,800
up ddaħħal fittizji jew biss data vojt
fis database tiegħek, li probabbilment

756
00:37:12,800 --> 00:37:15,450
mhux se tkun ħaġa tajba jekk
inti kienu qed jassumu li kien hemm.

757
00:37:15,450 --> 00:37:16,770
>> Allura dan huwa realtà annoying.

758
00:37:16,770 --> 00:37:19,890
Iżda b'mod ġenerali, client-side
validazzjoni hija kbira.

759
00:37:19,890 --> 00:37:21,810
Iżda jfisser darbtejn ħafna xogħol.

760
00:37:21,810 --> 00:37:25,970
Għalkemm hemm jeżistu diversi
libreriji, JavaScript libreriji għall-

761
00:37:25,970 --> 00:37:28,830
eżempju, li jagħmlu dan ħafna,
ħafna inqas ta 'ras.

762
00:37:28,830 --> 00:37:31,940
U inti tista 'użu mill-ġdid xi wħud mill-kodiċi
server-ġenb, client-side.

763
00:37:31,940 --> 00:37:35,980
Imma tirrealizza li huwa tipikament
xogħol addizzjonali.

764
00:37:35,980 --> 00:37:36,415
Yeah.

765
00:37:36,415 --> 00:37:37,792
>> UDJENZA: Mela jekk aħna biss
qal inqas sikura -

766
00:37:37,792 --> 00:37:39,205
>> DAVID J. Malan: [laughs]

767
00:37:39,205 --> 00:37:39,680
Ugh.

768
00:37:39,680 --> 00:37:43,105
Dawk huma dejjem l-aktar diffiċli
dawk li tingħata deċiżjoni.

769
00:37:43,105 --> 00:37:44,480
>> ROB BOWDEN: Li kieku
ġew aċċettati.

770
00:37:44,480 --> 00:37:44,810
>> DAVID J. Malan: What?

771
00:37:44,810 --> 00:37:45,810
>> ROB BOWDEN: I ħolqot din il-problema.

772
00:37:45,810 --> 00:37:46,735
Li ġew aċċettati.

773
00:37:46,735 --> 00:37:47,220
>> DAVID J. Malan: Yeah.

774
00:37:47,220 --> 00:37:47,830
>> UDJENZA: Kessaħ.

775
00:37:47,830 --> 00:37:51,770
>> ROB BOWDEN: Iżda aħna ma aċċettax
għall-ewwel waħda -

776
00:37:51,770 --> 00:37:53,630
ukoll, dak li aħna kienu qed ifittxu huwa
xi ħaġa bħal inti ma għandekx

777
00:37:53,630 --> 00:37:55,270
jikkomunikaw mal-server.

778
00:37:55,270 --> 00:37:58,355
Aħna ma jaċċettaw biss aktar malajr.

779
00:37:58,355 --> 00:38:00,080
>> UDJENZA: What about
ma rikarigu-paġna?

780
00:38:00,080 --> 00:38:00,430
>> ROB BOWDEN: Iva.

781
00:38:00,430 --> 00:38:03,000
Dan kien risposta aċċettata.

782
00:38:03,000 --> 00:38:06,300
>> DAVID J. Malan: xejn fejn ħassejna
kien aktar probabbli milli le probabbli

783
00:38:06,300 --> 00:38:09,780
li inti taf dak li inti kienu
qal, li hija iebsa

784
00:38:09,780 --> 00:38:13,500
linja li tiġbed kultant.

785
00:38:13,500 --> 00:38:16,000
Tintuża lista marbut minflok
ta 'firxa biex tinżamm

786
00:38:16,000 --> 00:38:17,590
magħżula lista tan-numri interi.

787
00:38:17,590 --> 00:38:21,000
Allura rasu aħna spiss jirreferu bl marbuta
listi li mmotivaw kollu tagħhom

788
00:38:21,000 --> 00:38:22,370
introduzzjoni kienet ikollok dinamiżmu.

789
00:38:22,370 --> 00:38:23,030
Huma jistgħu jikbru.

790
00:38:23,030 --> 00:38:23,950
Huma jistgħu tiċkien.

791
00:38:23,950 --> 00:38:27,370
Allura inti ma għandekx biex tiżdied permezz ta 'ċrieki
li attwalment joħolqu memorja aktar

792
00:38:27,370 --> 00:38:28,140
ma 'firxa.

793
00:38:28,140 --> 00:38:30,310
Jew inti ma għandekx biss
jgħidu, sorry, l-utent.

794
00:38:30,310 --> 00:38:31,410
Il-firxa hija mimlija.

795
00:38:31,410 --> 00:38:35,850
Tkabbir sabiex dinamiku tal-lista.

796
00:38:35,850 --> 00:38:37,210
A negattivi għalkemm listi marbuta?

797
00:38:37,210 --> 00:38:40,916

798
00:38:40,916 --> 00:38:43,356
>> UDJENZA: Huwa lineari.

799
00:38:43,356 --> 00:38:45,800
Tiftix fuq il-lista marbuta hija lineari
minflok ta 'dak li inti log pulzieri

800
00:38:45,800 --> 00:38:46,360
>> DAVID J. Malan: Eżattament.

801
00:38:46,360 --> 00:38:50,160
Tiftix fuq lista marbuta ma huwa lineari,
anki jekk huwa magħżula, għaliex inti tista '

802
00:38:50,160 --> 00:38:53,170
biss issegwi dawn frak tal-ħobż, dawn
pointers, mill-bidu tal-lista

803
00:38:53,170 --> 00:38:53,570
sa l-aħħar.

804
00:38:53,570 --> 00:38:57,970
Inti ma tistax lieva aċċess bl-addoċċ u,
B'hekk, it-tiftix binarju, anki jekk huwa

805
00:38:57,970 --> 00:39:00,740
magħżula, li inti tista '
tagħmel ma 'firxa.

806
00:39:00,740 --> 00:39:02,390
U hemm ukoll spejjeż oħra.

807
00:39:02,390 --> 00:39:02,966
Yeah.

808
00:39:02,966 --> 00:39:03,800
>> UDJENZA: Memorja ineffiċjenti?

809
00:39:03,800 --> 00:39:04,130
>> DAVID J. Malan: Yeah.

810
00:39:04,130 --> 00:39:06,940
Well, I mhux bilfors
jgħidu ineffiċjenti.

811
00:39:06,940 --> 00:39:10,110
Iżda dan ma jiswik memorja aktar,
għaliex ikollok bżonn 32 bits għal kull

812
00:39:10,110 --> 00:39:13,400
node għall-pointer addizzjonali, fi
inqas għal lista marbuta weħidhom.

813
00:39:13,400 --> 00:39:16,660
Issa, jekk int biss ħażna interi u
int żżid il-pointer, li

814
00:39:16,660 --> 00:39:17,830
fil-fatt tip ta 'non-trivjali.

815
00:39:17,830 --> 00:39:19,340
Huwa irduppjar tal-ammont tal-memorja.

816
00:39:19,340 --> 00:39:22,330
Iżda fir-realtà, jekk int jaħżen
lista marbuta ta structs li jista 'jkollhom

817
00:39:22,330 --> 00:39:25,540
8 bytes, 16 bytes, saħansitra aktar
minn dan, forsi huwa inqas

818
00:39:25,540 --> 00:39:26,500
ta 'spejjeż marġinali.

819
00:39:26,500 --> 00:39:28,320
Imma hija spiża xorta.

820
00:39:28,320 --> 00:39:31,880
Dan jew ta 'dawk stajt
Kien multa bħala negattivi.

821
00:39:31,880 --> 00:39:32,110
>> 18.

822
00:39:32,110 --> 00:39:36,100
Bl-użu PHP minflok C li tikteb
programm kmand tal-linja.

823
00:39:36,100 --> 00:39:41,890
So here, huwa spiss aktar malajr li jużaw
lingwa bħal PHP jew Ruby jew Python.

824
00:39:41,890 --> 00:39:43,700
Inti biss malajr tiftaħ
up editur test.

825
00:39:43,700 --> 00:39:45,900
Inti għandek bosta funzjonijiet aktar
disponibbli lilek.

826
00:39:45,900 --> 00:39:49,325
PHP għandha l-sink tal-kċina tal-funzjonijiet,
billi fis-C, inti

827
00:39:49,325 --> 00:39:50,420
jkollhom ħafna, ftit li xejn.

828
00:39:50,420 --> 00:39:53,820
Fil-fatt, guys l jafu l-mod iebes
li inti ma għandekx tabelli hash.

829
00:39:53,820 --> 00:39:55,000
Inti ma rabtu listi.

830
00:39:55,000 --> 00:39:57,470
Jekk inti tixtieq dawn, inti għandek
jimplimentawhom yourself.

831
00:39:57,470 --> 00:40:00,950
>> Allura rasu wieħed mill PHP jew verament xi
lingwa interpretat hija l-ħeffa

832
00:40:00,950 --> 00:40:02,920
li magħhom inti tista 'jikteb il-kodiċi.

833
00:40:02,920 --> 00:40:06,660
Iżda żvantaġġ, rajna dan meta I
malajr bit-tarjola up a misspeller

834
00:40:06,660 --> 00:40:11,780
implimentazzjoni fl lecture jużaw PHP, huwa
li l-użu ta 'lingwa interpretat

835
00:40:11,780 --> 00:40:13,570
huwa normalment aktar kajman.

836
00:40:13,570 --> 00:40:18,420
U rajna li b'mod ċar ma '
żieda fil-ħin minn 0.3 sekondi għal 3

837
00:40:18,420 --> 00:40:24,440
sekondi, minħabba l-interpretazzjoni
li attwalment jiġri.

838
00:40:24,440 --> 00:40:27,060
>> Rasu ieħor kien li inti
ma għandekx biex jikkompilaw.

839
00:40:27,060 --> 00:40:30,130
Għalhekk wkoll tħaffef l-iżvilupp
inċidentalment, għaliex inti ma għandekx

840
00:40:30,130 --> 00:40:31,360
żewġ passi lejn tmexxija ta 'programm.

841
00:40:31,360 --> 00:40:32,140
Inti biss għandek wieħed.

842
00:40:32,140 --> 00:40:35,260
U hekk dan huwa pretty
konvinċenti kif ukoll.

843
00:40:35,260 --> 00:40:38,450
Permezz ta 'database SQL minflok
fajl CSV li jaħżen data.

844
00:40:38,450 --> 00:40:40,230
Database hekk SQL huwa użat għall pset7.

845
00:40:40,230 --> 00:40:42,060
CSV fajls li inti ma jużawx ħafna.

846
00:40:42,060 --> 00:40:45,960
Imma inti użati indirettament pset7 bħala
ukoll billi tkellem lill Yahoo Finanzi.

847
00:40:45,960 --> 00:40:49,330
>> Iżda CSV huwa bħad fajl Excel iżda
super sempliċi, fejn il-kolonni huma

848
00:40:49,330 --> 00:40:54,010
biss demarked b'virgoli ġewwa
ta 'fajl test mod ieħor.

849
00:40:54,010 --> 00:40:56,740
U l-użu ta 'database SQL hija
ftit aktar konvinċenti.

850
00:40:56,740 --> 00:41:00,060
Huwa ta 'rasu, għaliex inti tikseb l-affarijiet
bħall tagħżel u daħħal u ħassar.

851
00:41:00,060 --> 00:41:03,790
U ikollok, preżumibbilment, l-indiċi li
MySQL u databases oħra, bħal

852
00:41:03,790 --> 00:41:07,510
Oracle, jibnu għalik fil-memorja, li
ifisser tagħżel tiegħek probabbilment ma jkunx

853
00:41:07,510 --> 00:41:09,000
se tkun top lineari għal isfel.

854
00:41:09,000 --> 00:41:11,300
Huwa fil-fatt se tkun xi ħaġa
bħal tfittxija binarju jew xi ħaġa

855
00:41:11,300 --> 00:41:12,520
simili fl-ispirtu.

856
00:41:12,520 --> 00:41:13,930
Allura dawn qed ġeneralment aktar malajr.

857
00:41:13,930 --> 00:41:16,040
>> Iżda tnaqqis hija li
huwa biss aktar xogħol.

858
00:41:16,040 --> 00:41:16,730
Huwa aktar sforz.

859
00:41:16,730 --> 00:41:18,140
Għandek tifhem databases.

860
00:41:18,140 --> 00:41:18,940
Inti għandek li din tintrama.

861
00:41:18,940 --> 00:41:20,840
Ikollok bżonn ta 'server jiddekorri
li database fuq.

862
00:41:20,840 --> 00:41:22,750
Inti jeħtieġ li jifhmu
kif kkonfigurat.

863
00:41:22,750 --> 00:41:24,930
Allura dawn huma biss dawn
tipi ta 'kompromessi.

864
00:41:24,930 --> 00:41:27,860
Billi fajl CSV, inti tista '
joħolqu dan ma gedit.

865
00:41:27,860 --> 00:41:28,770
U int tajba biex tmur.

866
00:41:28,770 --> 00:41:31,550
M'hemm l-ebda kumplessità lil hinn minnha.

867
00:41:31,550 --> 00:41:34,870
>> Permezz ta 'trie minflok ta' tabella hash
ma 'chaining separat li jaħżen

868
00:41:34,870 --> 00:41:37,490
dizzjunarju ta 'kliem reminixxenti
ta pset5.

869
00:41:37,490 --> 00:41:42,480
Allura jipprova rasu, fit-teorija
għall-inqas, huwa dak?

870
00:41:42,480 --> 00:41:46,380
Ħin kostanti, għall-inqas jekk int
hashing fuq kull wieħed mill-individwu

871
00:41:46,380 --> 00:41:48,990
ittri fil-kelma, bħalek
jista 'jkollhom għall pset5.

872
00:41:48,990 --> 00:41:52,720
Li jista 'jkun ta' ħames hashes, sitt
hashes jekk hemm ħames jew sitt

873
00:41:52,720 --> 00:41:53,900
ittri fil-kelma.

874
00:41:53,900 --> 00:41:54,580
U li pjuttost tajba.

875
00:41:54,580 --> 00:41:56,910
U jekk hemm xi rbit għoli dwar kif
twil kliem tiegħek jista 'jkun, li l-

876
00:41:56,910 --> 00:41:59,320
żmien tassew asimptotikalment kostanti.

877
00:41:59,320 --> 00:42:05,180
>> Billi tabella hash ma separata
ikkatenar, il-problema hemmhekk ma 'dak

878
00:42:05,180 --> 00:42:09,070
tip ta 'struttura data huwa li l-
prestazzjoni ta 'algoritmi tiegħek normalment

879
00:42:09,070 --> 00:42:12,700
jiddependi min-numru ta 'affarijiet
diġà fl-istruttura tad-data.

880
00:42:12,700 --> 00:42:15,660
U li definittivament il-każ ma
ktajjen, fejn l-għalf aktar inti tpoġġi

881
00:42:15,660 --> 00:42:18,800
fis-tabella hash, l-itwal dawk
ktajjen imorru, li jfisser fl-agħar

882
00:42:18,800 --> 00:42:21,960
każ, il-ħaġa inti tista 'tfittex għal
huwa it-triq kollha fl-aħħar ta 'wieħed

883
00:42:21,960 --> 00:42:26,000
dawn in-netwerks, li effettivament
jaqa 'fis xi ħaġa lineari.

884
00:42:26,000 --> 00:42:29,450
>> Issa, fil-prattika, jista assolutament
jkun il-każ li tabella hash ma

885
00:42:29,450 --> 00:42:32,820
ktajjen hija aktar mgħaġġla minn korrispondenti
implimentazzjoni trie.

886
00:42:32,820 --> 00:42:35,570
Iżda li għal diversi raġunijiet, fost
li jipprova juża lott kollu ta '

887
00:42:35,570 --> 00:42:39,240
memorja li jistgħu, fil-fatt, l-affarijiet bil-mod
isfel, għaliex inti ma tieħux sbieħ

888
00:42:39,240 --> 00:42:42,410
benefiċċji ta 'xi ħaġa imsejħa caching,
fejn l-affarijiet li huma qrib flimkien

889
00:42:42,410 --> 00:42:45,420
fil-memorja tista 'tkun aċċessata
spiss aktar malajr.

890
00:42:45,420 --> 00:42:48,180
U xi kultant inti tista 'toħroġ bi
funzjoni hash verament tajba.

891
00:42:48,180 --> 00:42:51,060
Anki jekk għandek l-iskart daqsxejn ta '
memorja, inti tista ', tabilħaqq, tkun tista'

892
00:42:51,060 --> 00:42:54,430
isibu affarijiet malajr u mhux
ħażin kif linearment.

893
00:42:54,430 --> 00:42:58,410
>> Għalhekk fil-qosor, ma kienx hemm neċessarjament
ma 'kwalunkwe minn dawn wieħed jew saħansitra tnejn

894
00:42:58,410 --> 00:43:00,050
affarijiet speċifiċi aħna kienu qed ifittxu.

895
00:43:00,050 --> 00:43:03,080
Really xejn konvinċenti
bħala pożittivi u negattivi

896
00:43:03,080 --> 00:43:04,800
ġeneralment maqbuda għajn tagħna.

897
00:43:04,800 --> 00:43:11,840
>> ROB BOWDEN: Dan għall-rasu, għamilna
ma jaċċettawx waħdu "aktar malajr." You

898
00:43:11,840 --> 00:43:14,540
kellhom jgħidu xi ħaġa dwar dan.

899
00:43:14,540 --> 00:43:17,910
Anke jekk inti qal teoretikament aktar mgħaġġla,
aħna kien jaf li inti tip ta 'mifhuma

900
00:43:17,910 --> 00:43:19,470
li huwa 0 tar 1.

901
00:43:19,470 --> 00:43:22,820
U tabella hash, fit-teorija,
mhuwiex 0 ta '1.

902
00:43:22,820 --> 00:43:26,550
Isemmi xejn dwar runtime
ġeneralment ltqajna inti l-punti.

903
00:43:26,550 --> 00:43:32,640
Imma "aktar malajr," ħafna mill-soluzzjonijiet fuq
il-bord kbir li jipprova kienu ġew

904
00:43:32,640 --> 00:43:34,990
oġġettivament aktar kajman minn soluzzjonijiet
li kienu tabelli hash.

905
00:43:34,990 --> 00:43:37,250
Allura aktar mgħaġġel u fih innifsu
mhuwiex verament veru.

906
00:43:37,250 --> 00:43:41,550

907
00:43:41,550 --> 00:43:44,380
>> DAVID J. Malan: Dom de dom dom.

908
00:43:44,380 --> 00:43:46,686
Jien probabbilment l-unika waħda li jirrealizza
li kif li suppost

909
00:43:46,686 --> 00:43:47,500
jiġi ppronunzjat, right?

910
00:43:47,500 --> 00:43:50,400
>> ROB BOWDEN: I kellhom attwalment l-ebda idea.

911
00:43:50,400 --> 00:43:51,650
>> DAVID J. Malan: Huwa magħmul
sens in my head.

912
00:43:51,650 --> 00:43:53,830

913
00:43:53,830 --> 00:43:57,580
>> ROB BOWDEN: jien tagħmel dan wieħed.

914
00:43:57,580 --> 00:43:58,020
OK.

915
00:43:58,020 --> 00:44:04,243
Allura dan huwa l-waħda fejn inti kellha tfassal
-dijagramma simili inti tista '

916
00:44:04,243 --> 00:44:06,040
raw fuq eżamijiet passat.

917
00:44:06,040 --> 00:44:12,200
Mela ejja biss ħarsa lejn dan.

918
00:44:12,200 --> 00:44:18,170
Allura mill-node HTML, għandna żewġ
tfal, ir-ras u l-ġisem.

919
00:44:18,170 --> 00:44:20,570
Allura aħna fergħa - ras u l-ġisem.

920
00:44:20,570 --> 00:44:22,280
Il-kap għandu tag titolu.

921
00:44:22,280 --> 00:44:23,710
Allura aħna għandna titolu.

922
00:44:23,710 --> 00:44:28,450
>> Issa, l-unika ħaġa li ħafna nies
nesa hija li dawn lymph test huma

923
00:44:28,450 --> 00:44:30,430
elementi fi ħdan din is-siġra.

924
00:44:30,430 --> 00:44:36,260
So here we jiġri li tiġbed minnhom bħala ovali
li jiddistingwihom minn dawn

925
00:44:36,260 --> 00:44:37,380
tipi ta 'nodes.

926
00:44:37,380 --> 00:44:41,450
Imma avviż wkoll hawnhekk għandna top,
tan-nofs, u fil-qiegħ se jispiċċaw

927
00:44:41,450 --> 00:44:42,560
lymph test.

928
00:44:42,560 --> 00:44:46,250
Allura jinsa dawk kien kemmxejn
ta 'żball komuni.

929
00:44:46,250 --> 00:44:48,770
>> Il-korp għandu tlett itfal -
dawn it-tliet divs.

930
00:44:48,770 --> 00:44:53,340
Allura div, div, div u mbagħad it-test
tfal node ta 'dawk divs.

931
00:44:53,340 --> 00:44:55,900
Li pjuttost ħafna huwa
għal dak il-mistoqsijiet.

932
00:44:55,900 --> 00:44:57,860
>> DAVID J. Malan: U huwa ta 'min jinnota,
anke jekk aħna ma nitkellem fuq dawn

933
00:44:57,860 --> 00:45:01,040
dettalji fil-ħin aħna jonfqu fuq
JavaScript, li l-ordni ma, fil-

934
00:45:01,040 --> 00:45:02,290
fatt, kwistjoni teknikament.

935
00:45:02,290 --> 00:45:06,330
Mela jekk head jasal quddiem korp fil-
HTML, allura dan għandu jidher li l-

936
00:45:06,330 --> 00:45:08,860
xellug tal-ġisem fil-DOM attwali.

937
00:45:08,860 --> 00:45:12,265
Li tiegħu huwa, b'mod ġenerali, biss FYI,
xi ħaġa imsejħa ordni dokument, fejn

938
00:45:12,265 --> 00:45:13,260
dan ma materja.

939
00:45:13,260 --> 00:45:17,470
U jekk inti kienu qed jimplimentaw parser,
a program li taqra HTML fil-bini

940
00:45:17,470 --> 00:45:20,960
l-siġra fil-memorja, li tkun onest,
dan huwa intuwittivament probabbilment dak li inti

941
00:45:20,960 --> 00:45:24,720
jagħmlu xorta waħda - fuq għal isfel,
xellug għal-lemin.

942
00:45:24,720 --> 00:45:26,116
>> ROB BOWDEN: Mistoqsijiet dwar li?

943
00:45:26,116 --> 00:45:29,080

944
00:45:29,080 --> 00:45:30,000
Nagħmel dak li jmiss?

945
00:45:30,000 --> 00:45:32,380
>> DAVID J. Malan: Sure.

946
00:45:32,380 --> 00:45:33,810
>> ROB BOWDEN: OK.

947
00:45:33,810 --> 00:45:39,320
Allura dan huwa l-buffer qbiż
kwistjoni attakk.

948
00:45:39,320 --> 00:45:43,740
Il-ħaġa prinċipali li jirrikonoxxu hawnhekk hija,
ukoll, kif jista trick avversarju

949
00:45:43,740 --> 00:45:46,170
dan il-programm fis eżekuzzjoni
kodiċi arbitrarja?

950
00:45:46,170 --> 00:45:51,860
Allura argv1, l-ewwel linja tal-kmand
argument li dan il-programm, li jista 'jkun

951
00:45:51,860 --> 00:45:53,920
twil arbitrarju.

952
00:45:53,920 --> 00:45:59,160
Iżda hawnhekk aħna qed jużaw memcpy li kopja
argv1, li hawnhekk huwa bar.

953
00:45:59,160 --> 00:46:00,165
Aħna qed tgħaddi bħala l-argument.

954
00:46:00,165 --> 00:46:02,050
U għalhekk huwa tieħu fuq l-isem bar.

955
00:46:02,050 --> 00:46:08,040
>> Allura aħna qed memcpying bar
fis dan buffer c.

956
00:46:08,040 --> 00:46:09,400
Kemm bytes aħna ikkupjar?

957
00:46:09,400 --> 00:46:14,040
Well bytes bar iżda ħafna jiġri li
tkun qed tuża, it-tul ta 'dan l-argument.

958
00:46:14,040 --> 00:46:17,930
Iżda c huwa biss 12 bytes wiesgħa.

959
00:46:17,930 --> 00:46:22,280
Allura jekk aħna tip ta 'argument linja tal-kmand
dan huwa itwal minn 12 bytes, aħna qed

960
00:46:22,280 --> 00:46:25,470
se jfur dan
partikolari buffer.

961
00:46:25,470 --> 00:46:31,000
Issa, kif jista 'avversarju trick l-
programm fis eżekuzzjoni kodiċi arbitrarja?

962
00:46:31,000 --> 00:46:34,910
>> Mela ftakar li hawn
prinċipali qed titlob foo.

963
00:46:34,910 --> 00:46:37,340
U hekk allura sejħiet ewlenin foo.

964
00:46:37,340 --> 00:46:40,408
Ejja tiġbed.

965
00:46:40,408 --> 00:46:44,720

966
00:46:44,720 --> 00:46:46,990
Allura aħna għandna munzell tagħna.

967
00:46:46,990 --> 00:46:49,090
U prinċipali għandha qafas stack
fil-qiegħ.

968
00:46:49,090 --> 00:46:51,860

969
00:46:51,860 --> 00:46:53,250
F'xi punt, sejħiet ewlenin foo.

970
00:46:53,250 --> 00:46:55,390
Well, immedjatament, sejħiet ewlenin foo.

971
00:46:55,390 --> 00:46:57,130
U hekk foo gets frame munzell tagħha stess.

972
00:46:57,130 --> 00:46:59,650

973
00:46:59,650 --> 00:47:02,220
>> Issa, f'xi punt, foo
se jirritorna.

974
00:47:02,220 --> 00:47:06,810
U marru prospetti foo, għandna bżonn inkunu nafu fuq
liema linja tal-kodiċi ġewwa ta ewlenin li għandna

975
00:47:06,810 --> 00:47:10,610
kienu sabiex tkun taf fejn
għandna jerġgħu jibdew fi prinċipali.

976
00:47:10,610 --> 00:47:13,100
Nistgħu sejħa foo minn kollu
mazz ta 'postijiet differenti.

977
00:47:13,100 --> 00:47:14,620
Kif inkunu nafu fejn jirritornaw?

978
00:47:14,620 --> 00:47:16,460
Well, għandna bżonn li taħżen din x'imkien.

979
00:47:16,460 --> 00:47:23,010
>> Allura x'imkien dritt madwar hawn, aħna maħżen
fejn aħna għandhom imorru lura għal darba

980
00:47:23,010 --> 00:47:24,070
prospetti foo.

981
00:47:24,070 --> 00:47:26,350
U dan huwa l-indirizz ta 'ritorn.

982
00:47:26,350 --> 00:47:30,490
Allura kif avversarju jista 'jieħu vantaġġ
ta 'dan huwa l-fatt li

983
00:47:30,490 --> 00:47:37,550
dan buffer c jiġi maħżun, ejja
jgħidu, dritt hawn huwa ċ.

984
00:47:37,550 --> 00:47:39,690
Allura konna ltqajna 12 bytes għal c.

985
00:47:39,690 --> 00:47:40,540
Dan huwa ċ.

986
00:47:40,540 --> 00:47:43,030
U dan huwa ċirku munzell foo tal.

987
00:47:43,030 --> 00:47:49,970
Mela jekk l-utent malizzjużi jidħol aktar
bytes minn 12 jew jidħlu kmand

988
00:47:49,970 --> 00:47:54,570
argument linja li l-aktar minn 12
karattri, allura aħna qed tmur biex

989
00:47:54,570 --> 00:47:57,540
overflow dan buffer.

990
00:47:57,540 --> 00:47:59,910
>> Nistgħu jibqgħu għaddejjin.

991
00:47:59,910 --> 00:48:02,220
U f'xi punt, aħna tmur ferm
biżżejjed li nibdew

992
00:48:02,220 --> 00:48:05,120
kitba fuq dan l-indirizz ta 'ritorn.

993
00:48:05,120 --> 00:48:08,310
Allura ladarba aħna jissostitwixxu l-indirizz ta 'ritorn,
dan ifisser li meta foo

994
00:48:08,310 --> 00:48:14,220
prospetti, aħna qed jirritornaw lejn kull fejn il-
utent malizzjużi huwa javżak li minn

995
00:48:14,220 --> 00:48:19,490
kwalunkwe valur daħal, b'kull
karattru l-utent daħal.

996
00:48:19,490 --> 00:48:24,320
U għalhekk jekk l-utent malizzjużi qed
partikolarment għaqlija, huwa jista 'jkollhom dan

997
00:48:24,320 --> 00:48:29,255
ritorn lejn x'imkien fil-printDef
funzjoni jew x'imkien fil-malloc

998
00:48:29,255 --> 00:48:31,830
funzjoni, biss kullimkien arbitrarja.

999
00:48:31,830 --> 00:48:38,420
>> Iżda anke aktar għaqlija huwa dak jekk ikollu
l-utent ritorn lejn dritt hawn.

1000
00:48:38,420 --> 00:48:41,920
U mbagħad tibda eżekuzzjoni
dawn bħala linji ta 'kodiċi.

1001
00:48:41,920 --> 00:48:46,610
Allura f'dak il-punt, l-utent jista 'jidħol
kull ma trid f'dan ir reġjun.

1002
00:48:46,610 --> 00:48:52,210
U hu għandu kontroll sħiħ
il-programm tiegħek.

1003
00:48:52,210 --> 00:48:53,460
Mistoqsijiet dwar li?

1004
00:48:53,460 --> 00:48:56,380

1005
00:48:56,380 --> 00:49:00,970
Allura l-mistoqsija li jmiss hija kompluta l-
implementazzjoni ġdida ta foo b'tali mod

1006
00:49:00,970 --> 00:49:02,620
li huwa m'għadux vulnerabbli.

1007
00:49:02,620 --> 00:49:03,870
>> Hekk hemm koppja ta 'modi
li seta 'jsir dan.

1008
00:49:03,870 --> 00:49:10,900

1009
00:49:10,900 --> 00:49:13,330
Għad għandna c biss
benesseri ta 'tul ta' 12.

1010
00:49:13,330 --> 00:49:16,480
Inti tista inbidlu dan
bħala parti mill-soluzzjoni tiegħek.

1011
00:49:16,480 --> 00:49:18,930
Aħna wkoll miżjuda verifika biex tagħmel
żgur bar ma kienx null.

1012
00:49:18,930 --> 00:49:24,460
Għalkemm inti ma bżonn
li għal kreditu sħiħa.

1013
00:49:24,460 --> 00:49:27,690
Allura aħna qed iċċekkjar ewwel l-
tul sensiela ta 'bar.

1014
00:49:27,690 --> 00:49:31,650
Jekk huwa akbar minn 12, imbagħad
ma attwalment jagħmlu l-kopja.

1015
00:49:31,650 --> 00:49:33,010
Allura dak mod wieħed ta 'iffissar.

1016
00:49:33,010 --> 00:49:36,750
>> Mod ieħor ta 'iffissar huwa minflok
jkollhom c jkunu biss ta tul ta '12, li huwa

1017
00:49:36,750 --> 00:49:39,310
jkun ta 'tul strlen (bar).

1018
00:49:39,310 --> 00:49:43,370
Mod ieħor ta 'iffissar huwa
li attwalment biss ritorn.

1019
00:49:43,370 --> 00:49:46,690
Mela jekk kellek biss gotten rid ta 'kollha ta'
dan, jekk kellek biss mħassra kollha

1020
00:49:46,690 --> 00:49:51,830
linji ta 'kodiċi, inti tkun gotten
kreditu sħiħa, peress li din il-funzjoni

1021
00:49:51,830 --> 00:49:54,150
attwalment ma twettaq xejn.

1022
00:49:54,150 --> 00:49:57,650
Huwa ikkupjar kmand tal-linja
argument fis xi array b'mod

1023
00:49:57,650 --> 00:49:59,960
frame munzell lokali tiegħu.

1024
00:49:59,960 --> 00:50:01,310
U allura l-ħaġa huwa jirritorna.

1025
00:50:01,310 --> 00:50:04,020
U tkun xi jitlestew hija marret.

1026
00:50:04,020 --> 00:50:09,740
Allura ritorn kien ukoll suffiċjenti
mod ta 'jkollna kreditu sħiħa.

1027
00:50:09,740 --> 00:50:13,425
>> DAVID J. Malan: Mhux pjuttost l-ispirtu ta '
il-kwistjoni iżda aċċettabbli kull l-

1028
00:50:13,425 --> 00:50:15,580
spec xorta.

1029
00:50:15,580 --> 00:50:18,260
>> ROB BOWDEN: Mistoqsijiet dwar xi li?

1030
00:50:18,260 --> 00:50:22,270
L-unika ħaġa li għandek inqas
meħtieġa li kompilazzjoni kodiċi.

1031
00:50:22,270 --> 00:50:24,810
Allura anke jekk teknikament m'intix
vulnerabbli jekk il-kodiċi tiegħek ma

1032
00:50:24,810 --> 00:50:29,130
jikkumpilaw, aħna ma jaċċettaw li.

1033
00:50:29,130 --> 00:50:31,350
Ebda mistoqsijiet?

1034
00:50:31,350 --> 00:50:33,320
OK.

1035
00:50:33,320 --> 00:50:34,580
>> DAVID J. Malan: Tixtieq
jiġifieri dan it-titolu?

1036
00:50:34,580 --> 00:50:37,230
>> ROB BOWDEN: Le

1037
00:50:37,230 --> 00:50:40,470
>> DAVID J. Malan: Allura f'dan il-wieħed, dan
kien jew aħbar tajba jew aħbar ħażina.

1038
00:50:40,470 --> 00:50:43,870
Dan huwa litteralment l-istess problema
bħala l-ewwel kwizz.

1039
00:50:43,870 --> 00:50:46,140
U huwa kważi l-istess
problema pset1.

1040
00:50:46,140 --> 00:50:49,980
Iżda kien simplifikata apposta biex ikunu
piramida sempliċi, wieħed li jista 'jkun

1041
00:50:49,980 --> 00:50:52,330
solvuti bi ftit
iterazzjoni sempliċi.

1042
00:50:52,330 --> 00:50:55,680
U tassew, dak li konna jkollna fuq
hawn ma kienx daqstant il-loġika,

1043
00:50:55,680 --> 00:50:58,100
għaliex probabbilment, minn dan il-punt, int
aktar komdi milli suppost kienu

1044
00:50:58,100 --> 00:51:01,850
fil-ġimgħa ma 'għal loops jew għaliex loops,
imma verament tease apparti li

1045
00:51:01,850 --> 00:51:04,790
int ftit komda mal-
idea li PHP huwa mhux biss dwar dak

1046
00:51:04,790 --> 00:51:05,290
programmazzjoni.

1047
00:51:05,290 --> 00:51:07,820
Fil-fatt din tista 'tintuża bħala lingwa
biex jiktbu programmi linja tal-kmand.

1048
00:51:07,820 --> 00:51:10,060
>> U fil-fatt, dan huwa dak li aħna kienu qegħdin jippruvaw
niġbidlek l-attenzjoni għall.

1049
00:51:10,060 --> 00:51:12,060
Dan huwa programm PHP linja ta 'kmand.

1050
00:51:12,060 --> 00:51:16,690
So kodiċi C hawnhekk, filwaqt korretta
fis-C, mhux korretta għall PHP.

1051
00:51:16,690 --> 00:51:17,940
Iżda l-kodiċi huwa verament l-istess.

1052
00:51:17,940 --> 00:51:21,720
Jekk tqabbel l-soluzzjonijiet għall Quiz
0 kontra Quiz 1, inti ser issib li

1053
00:51:21,720 --> 00:51:25,630
huwa kważi identiku, ħlief għall-
xi sinjali dollaru u għall-

1054
00:51:25,630 --> 00:51:27,250
nuqqas ta 'tip data.

1055
00:51:27,250 --> 00:51:31,720
B'mod partikolari, jekk nieħdu ħarsa hawn,
tkun taf tara li aħna jtenni, f'dan

1056
00:51:31,720 --> 00:51:33,730
każ, mill-1 sa permezz 7.

1057
00:51:33,730 --> 00:51:34,910
>> Aħna seta 'jsir indiċi 0.

1058
00:51:34,910 --> 00:51:37,320
Imma kultant, naħseb huwa biss
mentalment aktar faċli li wieħed jaħseb dwar affarijiet

1059
00:51:37,320 --> 00:51:38,200
minn 1 sa 7.

1060
00:51:38,200 --> 00:51:40,300
Jekk inti tixtieq blokka waħda, imbagħad tnejn
blokki, imbagħad tlieta, imbagħad

1061
00:51:40,300 --> 00:51:41,770
dot, dot, dot seba.

1062
00:51:41,770 --> 00:51:45,960
Aħna j jiġu initialized 1
u mbagħad isserraħ fuq sa i.

1063
00:51:45,960 --> 00:51:48,150
U kollox hawnhekk huwa
inkella identiċi.

1064
00:51:48,150 --> 00:51:49,790
Iżda denja ta 'nota huma
koppja ta 'affarijiet.

1065
00:51:49,790 --> 00:51:53,230
Aħna nagħtuk dawn iż-żewġ linji, dan l-ewwel
waħda, goofily imsemmi bħala shebang

1066
00:51:53,230 --> 00:51:54,560
għall bang qawwija.

1067
00:51:54,560 --> 00:51:58,770
U li biss jispeċifika il-passaġġ, il-
folder, li fiha programm jista 'jkun

1068
00:51:58,770 --> 00:52:02,160
sabet li inti tixtieq li tuża
li tinterpreta dan il-fajl.

1069
00:52:02,160 --> 00:52:04,710
>> U allura l-linja wara li, ta '
naturalment, ifisser jidħol fil-modalità PHP.

1070
00:52:04,710 --> 00:52:07,740
U l-linja fil-qiegħ nett
ifisser modalità PHP ħruġ.

1071
00:52:07,740 --> 00:52:09,740
U dan jaħdem, b'mod ġenerali, ma
interpretat lingwi.

1072
00:52:09,740 --> 00:52:14,370
Huwa tip ta 'annoying jekk tikteb
programm fajl imsejjaħ foo.php.

1073
00:52:14,370 --> 00:52:17,320
U mbagħad utenti tiegħek għandek biss
ftakar, OK, biex imexxu dan il-programm, I

1074
00:52:17,320 --> 00:52:22,320
għandek tip "foo.php ispazju PHP." Kind
ta 'annoying jekk xejn.

1075
00:52:22,320 --> 00:52:25,270
U wkoll tiżvela dak il-programm tiegħek
huwa miktub fil-PHP, li mhux kollox

1076
00:52:25,270 --> 00:52:27,060
li jdawwal għall-utent.

1077
00:52:27,060 --> 00:52:30,100
>> Allura inti tista 'tneħħi l. PHP kollox
recall minn lecture.

1078
00:52:30,100 --> 00:52:35,690
U inti tista 'attwalment jagħmlu. / Foo jekk
inti stajt chmodded dan billi jagħmilha

1079
00:52:35,690 --> 00:52:36,500
eżekutibbli.

1080
00:52:36,500 --> 00:52:39,630
Allura chmod a + x foo kien jagħmel dan.

1081
00:52:39,630 --> 00:52:41,460
U jekk inti wkoll żżid il-shebang hawn.

1082
00:52:41,460 --> 00:52:45,320
Imma verament, il-problema ġiet jkollna fi
stampar xi ħaġa bħal din.

1083
00:52:45,320 --> 00:52:51,100
Nru HTML, ebda C-kodiċi ċertament,
biss ftit PHP.

1084
00:52:51,100 --> 00:52:54,100
Allura Milo mbagħad jintbagħat lura fil-problema 25.

1085
00:52:54,100 --> 00:52:58,050
U fl-25, inti ngħataw l-segwenti
kodiċi iskeletru, li kien

1086
00:52:58,050 --> 00:52:59,730
paġna web pretty sempliċi.

1087
00:52:59,730 --> 00:53:04,230
U l-parti mmerraq HTML għaqli kien jistabbilixxi
hawn, fejn għandna ġewwa tal-ġisem

1088
00:53:04,230 --> 00:53:09,160
forma li għandha ID unika ta 'inputs
ġewwa li minnhom kien żewġ inputs, wieħed

1089
00:53:09,160 --> 00:53:11,950
bl-idea ta 'isem, wieħed
bl-idea ta 'buttuna.

1090
00:53:11,950 --> 00:53:14,240
>> L-ewwel kien test tip, il-
tieni ta 'tip jissottomettu.

1091
00:53:14,240 --> 00:53:16,930
U hekk aħna taw inti, attwalment, aktar
ingredjenti milli għandek bżonn, biss hekk

1092
00:53:16,930 --> 00:53:19,230
inti guys kellhom għażliet li magħhom
biex issolvi din il-problema.

1093
00:53:19,230 --> 00:53:21,130
Inti ma għandekx bżonn strettament
kollha ta 'dawn IDs.

1094
00:53:21,130 --> 00:53:23,580
Iżda tippermetti li inti biex isolvu
b'modi differenti.

1095
00:53:23,580 --> 00:53:27,050
U fil-quċċata, avviż li
l-għan kien biex jiġu xprunati

1096
00:53:27,050 --> 00:53:27,960
tieqa bħal dan -

1097
00:53:27,960 --> 00:53:28,780
Hello, Milo! -

1098
00:53:28,780 --> 00:53:31,270
pop up fil-browser użu
sempliċi super, jekk

1099
00:53:31,270 --> 00:53:33,190
mhux ikrah, funzjoni ta 'twissija.

1100
00:53:33,190 --> 00:53:37,480
U għalhekk, finalment, dan jeħodna
kunċettwalment li b'xi mod jisimgħu għal

1101
00:53:37,480 --> 00:53:41,290
sottomissjonijiet tal-client-side forma
, Mhux il-ġenb server, b'xi

1102
00:53:41,290 --> 00:53:45,640
jirrispondu għal dik is-sottomissjoni mill-
ħtif-valur li l-utent ittajpjat

1103
00:53:45,640 --> 00:53:50,120
fil lill-qasam isem, u mbagħad
wiri fil-ġisem ta 'twissija.

1104
00:53:50,120 --> 00:53:53,460
>> Allura mod wieħed li inti tista 'tagħmel dan huwa ma
jQuery, li jistenna ftit

1105
00:53:53,460 --> 00:53:56,880
sintattikament mħawda fl-ewwel.

1106
00:53:56,880 --> 00:54:00,760
Tista 'tagħmel dan bil-kodiċi DOM pur -
document.getelement minn ID.

1107
00:54:00,760 --> 00:54:02,530
Iżda ejja tagħti ħarsa lejn din il-verżjoni.

1108
00:54:02,530 --> 00:54:05,110
I jkollhom koppja ta 'importanti
Linji ewwel.

1109
00:54:05,110 --> 00:54:09,460
Allura wieħed, aħna għandna din il-linja, li hija
identiku għal dak li inti tista raw

1110
00:54:09,460 --> 00:54:13,830
fil, nemmen, form2.html
mill-klassi fil-ġimgħa 9.

1111
00:54:13,830 --> 00:54:16,960
U dan huwa biss qal, jesegwixxu
il-kodiċi li ġejjin meta

1112
00:54:16,960 --> 00:54:18,430
d-dokument huwa lest.

1113
00:54:18,430 --> 00:54:21,770
Din hija importanti biss minħabba
Paġni HTML jinqraw fuq għal

1114
00:54:21,770 --> 00:54:23,280
qiegħ, xellug għal-lemin.

1115
00:54:23,280 --> 00:54:27,910
>> U għalhekk, jekk inti tipprova tagħmel
xi ħaġa fil-kodiċi up hawn biex xi DOM

1116
00:54:27,910 --> 00:54:31,560
element, xi tag HTML, li jistabbilixxi
hawn, int tagħmel wisq malajr,

1117
00:54:31,560 --> 00:54:34,220
minħabba li dan m'għandux lanqas
ġie moqri fil-memorja.

1118
00:54:34,220 --> 00:54:37,740
Allura billi qal dan document.ready
linja, aħna qed tgħid,

1119
00:54:37,740 --> 00:54:39,040
hawn xi kodiċi, browser.

1120
00:54:39,040 --> 00:54:42,440
Imma ma teżegwixxi dan sakemm il-sħiħ
dokument huwa lest, li hija l-DOM

1121
00:54:42,440 --> 00:54:44,320
siġra teżisti fil-memorja.

1122
00:54:44,320 --> 00:54:47,110
Dan huwa wieħed ftit aktar
sempliċi, jekk sintattikament a

1123
00:54:47,110 --> 00:54:51,890
daqsxejn differenti, fejn jien qal, grab
l-element HTML li unika

1124
00:54:51,890 --> 00:54:53,560
identifikatur inputs.

1125
00:54:53,560 --> 00:54:56,220
Dak hu l-tikketta hash
tindika, l-ID uniku.

1126
00:54:56,220 --> 00:54:58,070
U mbagħad jien sejħa. Jissottomettu.

1127
00:54:58,070 --> 00:55:01,660
>> So. Jissottomettu hawnhekk hija funzjoni, inkella
magħrufa bħala metodu, li l-

1128
00:55:01,660 --> 00:55:05,850
ġewwa tal-oġġett fuq it-naħa tax-xellug
naħa hemmhekk li I ma jenfasizzaw.

1129
00:55:05,850 --> 00:55:08,990
Mela jekk inti taħseb inputs bħala oġġett
fil-memorja - u tabilħaqq huwa.

1130
00:55:08,990 --> 00:55:10,440
Huwa node fil-siġra -

1131
00:55:10,440 --> 00:55:16,580
. Jissottomettu mezzi meta din il-formola ma '
din ID tiġi sottomessa, jesegwixxu

1132
00:55:16,580 --> 00:55:17,700
il-kodiċi li ġej.

1133
00:55:17,700 --> 00:55:20,290
I ma kura dak l-isem tal-
funzjoni huwa jien esekuzzjoni.

1134
00:55:20,290 --> 00:55:23,760
So here jien jużaw, bħal qabel, x'hemm
imsejjaħ il-funzjoni lambda jew

1135
00:55:23,760 --> 00:55:24,720
funzjoni anonima.

1136
00:55:24,720 --> 00:55:27,640
Mhuwiex fil-livelli kollha intellettwalment
interessanti oħra milli għandu l-ebda isem,

1137
00:55:27,640 --> 00:55:30,220
li huwa multa jekk int biss
qatt ser sejħa darba.

1138
00:55:30,220 --> 00:55:34,490
U hemm ġewwa I attwalment jimmaniġġaw
il-preżentazzjoni tal-formola.

1139
00:55:34,490 --> 00:55:36,810
I ewwel tiddikjara varjabbli
imsejħa valur.

1140
00:55:36,810 --> 00:55:40,610
U allura dak huwa l-effett ta 'din
enfasizzat porzjon hawn issa?

1141
00:55:40,610 --> 00:55:44,755
Dak li ma tagħmel fi
livell għoli għalija?

1142
00:55:44,755 --> 00:55:48,539
>> UDJENZA: Jiġrilha l-valur li l-
utent ma fil-HTML hawn taħt.

1143
00:55:48,539 --> 00:55:50,920
Jiġrilha li ID u mbagħad
isib il-valur ta 'dan.

1144
00:55:50,920 --> 00:55:51,590
>> DAVID J. Malan: Eżattament.

1145
00:55:51,590 --> 00:55:54,300
Hija grabs l-node, li l unika
identifikatur huwa l-isem.

1146
00:55:54,300 --> 00:55:56,900
Jiġrilha l-valur fihom, li
huwa, preżumibbilment, dak l-utent

1147
00:55:56,900 --> 00:55:58,190
ittajpjat lilu jew lilha nfisha.

1148
00:55:58,190 --> 00:56:01,020
U allura huwa jaħżen li fil-
varjabbli imsejħa valur.

1149
00:56:01,020 --> 00:56:03,720
Bħala twarrib, jista 'jkollok ukoll
għamlu dan ftit differenti.

1150
00:56:03,720 --> 00:56:09,250
Totally aċċettabbli billi tagħmel xi ħaġa
valur jinsabu var gets

1151
00:56:09,250 --> 00:56:10,500
document.getElementById.

1152
00:56:10,500 --> 00:56:12,860

1153
00:56:12,860 --> 00:56:15,460
U dan huwa għaliex huwa ftit
tedious li ma jużawx jQuery.

1154
00:56:15,460 --> 00:56:16,710
"Name". Valur.

1155
00:56:16,710 --> 00:56:18,330

1156
00:56:18,330 --> 00:56:19,620
Allura totalment aċċettabbli.

1157
00:56:19,620 --> 00:56:22,770
Modi differenti biex jagħmlu dan. jQuery biss
tendenza li jkunu ftit aktar konċiż u

1158
00:56:22,770 --> 00:56:25,230
definittivament aktar popolari
fost programmaturi.

1159
00:56:25,230 --> 00:56:27,590
>> Issa, jien tagħmel daqsxejn ta 'sanità
jivverifikaw, minħabba fil-problema

1160
00:56:27,590 --> 00:56:30,820
dikjarazzjoni aħna espliċitament qal, jekk il-
utent għadu ma ittajpjat tiegħu jew tagħha

1161
00:56:30,820 --> 00:56:32,580
isem, ma jurux allerti.

1162
00:56:32,580 --> 00:56:35,390
Iżda tista 'tiċċekkja għal dan, bi ftit
verifika għall-sekwenza vojta għal

1163
00:56:35,390 --> 00:56:37,850
quote-unquote jekk hemm
xejn fil-fatt hemmhekk.

1164
00:56:37,850 --> 00:56:40,880
Imma jekk mhuwiex ugwali għal kwotazzjoni-unquote,
I tixtieq li sejħa allerti.

1165
00:56:40,880 --> 00:56:45,610
U l-parti interessanti hawnhekk huwa li
aħna qed jużaw l-operatur plus, li

1166
00:56:45,610 --> 00:56:48,130
ma dak fl JavaScript?

1167
00:56:48,130 --> 00:56:48,740
Concatenate.

1168
00:56:48,740 --> 00:56:50,690
Allura huwa simili PHPs operatur dot.

1169
00:56:50,690 --> 00:56:52,820
Istess idea, sintassi kemmxejn differenti.

1170
00:56:52,820 --> 00:56:55,280
U jien biss joħolqu l-sekwenza li
inti raw fuq l-isparatura iskrin -

1171
00:56:55,280 --> 00:56:57,750
Hello, hekk u hekk.

1172
00:56:57,750 --> 00:56:59,200
>> U allura l-aħħar dettall huwa dan.

1173
00:56:59,200 --> 00:57:04,970
Why do I ritorn ġewwa falza
ta 'din il-funzjoni anonimi?

1174
00:57:04,970 --> 00:57:07,420
>> UDJENZA: M'hemm l-ebda valur.

1175
00:57:07,420 --> 00:57:09,380
You poġġih fil-forma.

1176
00:57:09,380 --> 00:57:12,320

1177
00:57:12,320 --> 00:57:16,730
Huwa biss jgħid, jekk il-valur ma jkunx
daqs blank, mbagħad jagħmluh.

1178
00:57:16,730 --> 00:57:20,040

1179
00:57:20,040 --> 00:57:20,940
Kien hemm vojt f'dak sottomissjoni.

1180
00:57:20,940 --> 00:57:21,170
>> DAVID J. Malan: OK.

1181
00:57:21,170 --> 00:57:21,640
Attenta għalkemm.

1182
00:57:21,640 --> 00:57:22,830
M'hemm l-ebda wieħed inkella hawn.

1183
00:57:22,830 --> 00:57:25,510
U li falza ritorn hija barra
tal-jekk il-kondizzjonijiet.

1184
00:57:25,510 --> 00:57:29,470
Allura din il-linja enfasizzat, ritorn foloz,
tesegwixxi x'ikun meta

1185
00:57:29,470 --> 00:57:32,310
il-formola tiġi sottomessa.

1186
00:57:32,310 --> 00:57:36,810
Dak ma jirritornaw ġewwa falza ta 'dan
handler avveniment, kif huwa msejjaħ,

1187
00:57:36,810 --> 00:57:38,450
l-avveniment inkwistjoni
jkunu sottomissjoni?

1188
00:57:38,450 --> 00:57:42,350

1189
00:57:42,350 --> 00:57:44,470
>> UDJENZA: Minħabba li
jiġri darba biss.

1190
00:57:44,470 --> 00:57:45,320
>> DAVID J. Malan: Biss jiġri darba.

1191
00:57:45,320 --> 00:57:46,821
Mhux pjuttost.

1192
00:57:46,821 --> 00:57:47,292
Yeah?

1193
00:57:47,292 --> 00:57:50,589
>> UDJENZA: Dan jipprevjeni l-forma minn
tippreżenta lill-imġieba default,

1194
00:57:50,589 --> 00:57:52,480
li jagħmlu l-rikarigu-paġna.

1195
00:57:52,480 --> 00:57:53,110
>> DAVID J. Malan: Eżattament.

1196
00:57:53,110 --> 00:57:56,490
Hekk jien tagħbija żejda-terminu jissottomettu hawn,
għaliex jien qal, il-formola hija

1197
00:57:56,490 --> 00:57:57,670
jiġi sottomess.

1198
00:57:57,670 --> 00:58:02,240
Imma kif inti jissuġġerixxu, huwa attwalment mhux
ġiet ippreżentata fil-mod HTTP veru.

1199
00:58:02,240 --> 00:58:06,870
Meta tikklikkja Submit, minħabba tagħna
handler onSubmit, aħna qed jinterċetta

1200
00:58:06,870 --> 00:58:09,040
dik is-sottomissjoni formola biex ngħidu hekk.

1201
00:58:09,040 --> 00:58:11,290
Aħna qed mbagħad tagħmel ħaġa tagħna
bil-kodiċi JavaScript.

1202
00:58:11,290 --> 00:58:14,070
Imma jien deliberatament jirritornaw falza,
għaliex dak li ma rridx li jiġri

1203
00:58:14,070 --> 00:58:18,430
qasma tat-tieni wara huwa għall-forma kollu
ruħha li jiġu sottomessi lill-web

1204
00:58:18,430 --> 00:58:22,800
server ma 'pari valur ewlenin billi jinbidlu
il-URL li tkun xi ħaġa simili

1205
00:58:22,800 --> 00:58:26,180
Q = il-qtates jew kwalunkwe għamilna,
per eżempju, fil-klassi.

1206
00:58:26,180 --> 00:58:29,640
Ma rridx li jiġri, għax
m'hemm l-ebda smigħ server għal dan

1207
00:58:29,640 --> 00:58:30,690
formola ta 'sottomissjoni.

1208
00:58:30,690 --> 00:58:32,320
Huwa purament isir fil-kodiċi JavaScript.

1209
00:58:32,320 --> 00:58:35,760
U hu għalhekk li I lanqas ikollhom
azzjoni attribut fuq formola tiegħi, minħabba I

1210
00:58:35,760 --> 00:58:38,870
ma intenzjoni biex dan
qatt tmur għall-server.

1211
00:58:38,870 --> 00:58:40,780
>> Għalhekk huwa qed sottomessa.

1212
00:58:40,780 --> 00:58:44,340
Iżda aħna qed jinterċetta dik il-formola
sottomissjoni u l-prevenzjoni tal-default

1213
00:58:44,340 --> 00:58:47,477
imġieba, li huwa li attwalment
jmorru it-triq kollha għall-server.

1214
00:58:47,477 --> 00:58:48,730
>> UDJENZA: Allura jżommuha client-side.

1215
00:58:48,730 --> 00:58:49,780
>> DAVID J. Malan: Żamma
-naħa tal-klijent dan.

1216
00:58:49,780 --> 00:58:51,030
Eżattament id-dritt.

1217
00:58:51,030 --> 00:58:53,240

1218
00:58:53,240 --> 00:58:55,757
Up li jmiss kien tiegħi oh MySQL.

1219
00:58:55,757 --> 00:59:00,000

1220
00:59:00,000 --> 00:59:00,430
>> ROB BOWDEN: OK.

1221
00:59:00,430 --> 00:59:04,990
Għalhekk din l-ewwel kwistjoni kienet ġeneralment
rough għall-persuni.

1222
00:59:04,990 --> 00:59:07,270
Għalkemm dawk aktar tard marru aħjar.

1223
00:59:07,270 --> 00:59:12,260
Allura inti kellhom jagħżlu l-data korretta
tipi kemm ta 'dawn il-kolonni.

1224
00:59:12,260 --> 00:59:17,750
U kemm ta 'dawn għandhom xi
affarijiet dwar minnhom li

1225
00:59:17,750 --> 00:59:20,620
jagħmlu l-għażla diffiċli.

1226
00:59:20,620 --> 00:59:24,430
Allura int ma kinitx valida
tip għal numru.

1227
00:59:24,430 --> 00:59:29,410
Ir-raġuni li kont 12-il ċifra
numru, l-int mhuwiex kbir biżżejjed biex

1228
00:59:29,410 --> 00:59:31,070
taħżen numri totali.

1229
00:59:31,070 --> 00:59:36,570
Allura għażla valida kien ikun kbir
int jekk jiġri li tkun taf li.

1230
00:59:36,570 --> 00:59:42,090
Ieħor għażla seta 'kien
qasam char ta 'tul ta' 12.

1231
00:59:42,090 --> 00:59:44,560
Allura kieku ħadmu waħda minn dawk.

1232
00:59:44,560 --> 00:59:46,100
Int ma.

1233
00:59:46,100 --> 00:59:50,170
>> Issa, il-bilanċ, think lura għall pset7.

1234
00:59:50,170 --> 00:59:59,540
Allura aħna speċifikament użati ta 'informazzjoni biex
jaħżnu l-valur tal-ishma jew -

1235
00:59:59,540 --> 01:00:00,550
>> DAVID J. Malan: Cash.

1236
01:00:00,550 --> 01:00:01,060
>> ROB BOWDEN: Cash.

1237
01:00:01,060 --> 01:00:05,710
Aħna użati ta 'informazzjoni biex jaħżnu l-ammont ta'
flus kontanti li l-utent bħalissa għandha.

1238
01:00:05,710 --> 01:00:10,950
Allura r-raġuni nagħmlu dan huwa
għaliex, ftakar, sufruni.

1239
01:00:10,950 --> 01:00:12,480
Hemm floating point fil-preċiżjoni.

1240
01:00:12,480 --> 01:00:18,200
Ma jistax jaħżen preċiżament l-flus
Valuri bħal rridu hawn.

1241
01:00:18,200 --> 01:00:23,630
Allura informazzjoni hija kapaċi preċiżament maħżen
xi ħaġa li, jgħidu, żewġ postijiet deċimali.

1242
01:00:23,630 --> 01:00:27,630
C'est pourquoi bilanċ, irridu
li jkunu ta 'informazzjoni u mhux float.

1243
01:00:27,630 --> 01:00:30,230
>> DAVID J. Malan: U wkoll, wisq, għalkemm
seta 'kien għaqlija f'pajjiżi oħra

1244
01:00:30,230 --> 01:00:32,760
kuntesti biex jaħsbu, forsi dan
hija opportunità għal int.

1245
01:00:32,760 --> 01:00:34,420
I ser biss iżommu kont ta '
affarijiet fil pennies.

1246
01:00:34,420 --> 01:00:38,670
Għaliex aħna wera b'mod espliċitu l-default
valur li jkunu 100.00, li

1247
01:00:38,670 --> 01:00:40,380
ifisser li tista 'biss tkun int.

1248
01:00:40,380 --> 01:00:45,310
U subtlety ieħor wisq bin-numru
kienet li ma kienx maħsub

1249
01:00:45,310 --> 01:00:46,180
li tkun kwistjoni trick.

1250
01:00:46,180 --> 01:00:49,860
Iżda tfakkar li int fil MySQL,
bħal fil-C, għall-inqas fil-

1251
01:00:49,860 --> 01:00:51,440
appliance, huwa 32-bit.

1252
01:00:51,440 --> 01:00:53,960
U anke jekk aħna ma jistennew li inti
taf eżattament kemm ċifri li

1253
01:00:53,960 --> 01:00:56,910
mezzi, do tfakkar li l-akbar numru
inti tista 'potenzjalment jirrappreżenta

1254
01:00:56,910 --> 01:01:00,710
ma 'numru 32-bit hija bejn wieħed u ieħor dak?

1255
01:01:00,710 --> 01:01:02,760
>> What numru nistgħu dejjem ngħid?

1256
01:01:02,760 --> 01:01:04,530
2 għall-32, li huwa dak li bejn wieħed u ieħor?

1257
01:01:04,530 --> 01:01:07,492

1258
01:01:07,492 --> 01:01:08,780
Inti ma għandekx tkun taf b'mod preċiż.

1259
01:01:08,780 --> 01:01:10,580
Imma bejn wieħed u ieħor huwa utli fil-ħajja.

1260
01:01:10,580 --> 01:01:12,200
Huwa madwar 4 biljuni.

1261
01:01:12,200 --> 01:01:14,430
Allura aħna ħadthom qal li għal xi ftit drabi.

1262
01:01:14,430 --> 01:01:16,360
I know I qal li għal xi ftit drabi.

1263
01:01:16,360 --> 01:01:17,670
U huwa madwar 4 biljuni.

1264
01:01:17,670 --> 01:01:19,710
U li l-istat tajjeb
ta 'thumb tkun taf.

1265
01:01:19,710 --> 01:01:21,880
Jekk għandek 8 bits, 256
huwa n-numru magic.

1266
01:01:21,880 --> 01:01:24,160
Jekk għandek 32 bits, 4
biljun jagħtu jew jieħu.

1267
01:01:24,160 --> 01:01:27,140
Mela jekk inti biss ikteb 4 biljuni,
tkun taf tara li huwa inqas ċifri minn

1268
01:01:27,140 --> 01:01:30,970
12, li jfisser li l-ċar ma
biżżejjed expressiveness jaqbad

1269
01:01:30,970 --> 01:01:34,220
Numru tal-kont 12 figuri.

1270
01:01:34,220 --> 01:01:34,940
>> ROB BOWDEN: OK.

1271
01:01:34,940 --> 01:01:38,520
Allura l-oħrajn marru aħjar.

1272
01:01:38,520 --> 01:01:40,900
Allura jissoponi li l-bank
timponi $ 20 kull xahar

1273
01:01:40,900 --> 01:01:42,400
ħlas ta 'manteniment fuq il-kontijiet kollha.

1274
01:01:42,400 --> 01:01:45,506
Ma 'dak SQL query tista' l-bank
tnaqqas $ 20 min kull għadd, anke jekk

1275
01:01:45,506 --> 01:01:47,520
jirriżulta f'xi bilanċi negattivi?

1276
01:01:47,520 --> 01:01:50,380
Allura bażikament, hemm erba '
tipi ewlenin ta 'mistoqsijiet -

1277
01:01:50,380 --> 01:01:52,840
daħħal, tagħżel, jaġġornaw, u ħassar.

1278
01:01:52,840 --> 01:01:56,080
Allura dak li aħna naħsbu li aħna qed
ser tuża hawn?

1279
01:01:56,080 --> 01:01:57,000
Aġġornament.

1280
01:01:57,000 --> 01:01:58,260
>> Mela ejja tagħti ħarsa.

1281
01:01:58,260 --> 01:02:04,290

1282
01:02:04,290 --> 01:02:05,870
So here we qed aġġornament.

1283
01:02:05,870 --> 01:02:09,900
Dak tabella huma we aġġornament kontijiet?

1284
01:02:09,900 --> 01:02:11,670
Allura aġġornament kontijiet.

1285
01:02:11,670 --> 01:02:15,390
U allura l-sintassi jgħid, liema
fil-kontijiet aħna aġġornament?

1286
01:02:15,390 --> 01:02:19,520
Well, aħna qed jistabbilixxu bilanċ ugwali għad-
valur kurrenti ta 'bilanċ minus 20.

1287
01:02:19,520 --> 01:02:22,860
Allura dan se taġġorna ringieli kollha
tal-kontijiet, jitnaqqas

1288
01:02:22,860 --> 01:02:26,250
$ 20 min-bilanċ.

1289
01:02:26,250 --> 01:02:29,260
>> DAVID J. Malan: A żball komuni hawn,
anke jekk aħna kultant ħaffru dan,

1290
01:02:29,260 --> 01:02:32,990
kien li attwalment ikollhom kodiċi PHP hawn
ssejjaħ il-funzjoni query jew it-tqegħid

1291
01:02:32,990 --> 01:02:35,460
kwotazzjonijiet madwar dak kollu li
ma kellhomx bżonn li jkun hemm.

1292
01:02:35,460 --> 01:02:39,780
>> ROB BOWDEN: Ftakar li MySQL hija
lingwa separat mill PHP.

1293
01:02:39,780 --> 01:02:42,410
Aħna jiġri li jkun miktub MySQL fil-PHP.

1294
01:02:42,410 --> 01:02:46,180
U PHP huwa mbagħad jibagħtuha
trasferiti għas-server MySQL.

1295
01:02:46,180 --> 01:02:51,120
Imma inti m'għandekx bżonn PHP sabiex
jikkomunikaw ma 'server MySQL.

1296
01:02:51,120 --> 01:02:51,730
>> DAVID J. Malan: Eżattament.

1297
01:02:51,730 --> 01:02:54,240
Allura l-ebda varjabbli b'sinjali dollaru
għandu jkun f'dan il-kuntest.

1298
01:02:54,240 --> 01:02:59,550
Hija tista 'biss tagħmel kollha ta' l-matematika
fid-database innifsu.

1299
01:02:59,550 --> 01:03:00,080
>> ROB BOWDEN: OK.

1300
01:03:00,080 --> 01:03:01,300
Allura dak li jmiss.

1301
01:03:01,300 --> 01:03:02,731
Huwa dan dak li jmiss?

1302
01:03:02,731 --> 01:03:03,210
Yeah.

1303
01:03:03,210 --> 01:03:06,570
Allura ma 'dak SQL query tista' l-bank
irkuprata l-numri tal-kont ta taghha

1304
01:03:06,570 --> 01:03:09,300
klijenti sinjuri, dawk bi
bilanċi akbar minn 1,000?

1305
01:03:09,300 --> 01:03:13,280
Allura liema mill-erba 'tipi ewlenin
aħna se tixtieq hawnhekk?

1306
01:03:13,280 --> 01:03:14,430
Agħżel.

1307
01:03:14,430 --> 01:03:16,650
Hekk irridu li tagħżel.

1308
01:03:16,650 --> 01:03:17,610
What do we trid tagħżel?

1309
01:03:17,610 --> 01:03:19,380
What kolonna irridu li tagħżel?

1310
01:03:19,380 --> 01:03:20,970
Aħna se tkun trid speċifikament
li tagħżel numru.

1311
01:03:20,970 --> 01:03:23,910
Imma jekk inti qal star, aħna
wkoll ammess.

1312
01:03:23,910 --> 01:03:25,820
>> Allura tagħżel numru minn dak tabella?

1313
01:03:25,820 --> 01:03:26,640
Kontijiet.

1314
01:03:26,640 --> 01:03:28,370
U allura l-kundizzjoni li rridu?

1315
01:03:28,370 --> 01:03:30,140
Fejn bilanċ akbar minn 1,000.

1316
01:03:30,140 --> 01:03:31,720
Aħna wkoll aċċettata akbar
minn jew ugwali.

1317
01:03:31,720 --> 01:03:35,230

1318
01:03:35,230 --> 01:03:36,190
Aħħar wieħed.

1319
01:03:36,190 --> 01:03:42,940
Ma 'dak SQL query tista' l-bank
qrib, jiġifieri, iħassru kull kont li

1320
01:03:42,940 --> 01:03:44,480
għandha bilanċ ta '$ 0?

1321
01:03:44,480 --> 01:03:47,620
Allura liema mill-erba aħna
tmur jridu jużaw?

1322
01:03:47,620 --> 01:03:48,320
Ħassar.

1323
01:03:48,320 --> 01:03:50,180
Allura l-sintassi għal dan?

1324
01:03:50,180 --> 01:03:51,890
Ħassar minn dak tabella?

1325
01:03:51,890 --> 01:03:53,550
Kontijiet.

1326
01:03:53,550 --> 01:03:55,790
U allura l-kondizzjoni li fuqha
irridu li jħassru -

1327
01:03:55,790 --> 01:03:57,280
fejn bilanċ ugwali żero.

1328
01:03:57,280 --> 01:04:03,050
Allura tħassar ringieli kollha mill-kontijiet
meta l-bilanċ huwa żero.

1329
01:04:03,050 --> 01:04:04,300
Mistoqsijiet dwar xi waħda minn dawn?

1330
01:04:04,300 --> 01:04:08,840

1331
01:04:08,840 --> 01:04:10,260
Trid kju?

1332
01:04:10,260 --> 01:04:11,200
>> DAVID J. Malan: gwida kju.

1333
01:04:11,200 --> 01:04:17,110
Allura f'dan il-wieħed, aħna ħadt kemmxejn
struttura familjari li aħna esplorati

1334
01:04:17,110 --> 01:04:20,450
daqsxejn fil-klassi flimkien ta structs,
li kienet data

1335
01:04:20,450 --> 01:04:21,910
struttura relatata fl-ispirtu.

1336
01:04:21,910 --> 01:04:24,670
Id-differenza għalkemm kju hija
li kellna li b'xi mod tiftakar li

1337
01:04:24,670 --> 01:04:27,900
kien fuq quddiem tal-kju, fil-kbar
parti b'tali mod li nistgħu nagħmlu aktar

1338
01:04:27,900 --> 01:04:30,530
użu effiċjenti tal-memorja, mill-inqas
jekk aħna kienu qed jużaw firxa.

1339
01:04:30,530 --> 01:04:35,460
>> Minħabba recall, jekk ikollna firxa, jekk,
per eżempju, dan huwa l-quddiem ta '

1340
01:04:35,460 --> 01:04:38,470
-kju, jekk I tikseb fis-kju hawn,
u mbagħad xi ħadd gets fil-linja

1341
01:04:38,470 --> 01:04:42,710
lura lili, wara me, lura lili, u
persuna waħda passi barra tal-linja, inti

1342
01:04:42,710 --> 01:04:45,930
tista ', kif rajna xi wħud mill-bniedem tagħna
voluntiera fil-klassi, ikollhom kulħadd

1343
01:04:45,930 --> 01:04:47,100
shift b'dan il-mod.

1344
01:04:47,100 --> 01:04:50,880
Iżda b'mod ġenerali, li jagħmlu kulħadd
xi ħaġa mhux l-aħjar użu tal-ħin

1345
01:04:50,880 --> 01:04:54,600
fi programm, għaliex dan ikun ifisser tiegħek
algoriżmu jkun qed jaħdem f'dak li

1346
01:04:54,600 --> 01:04:56,520
running time asintotiku?

1347
01:04:56,520 --> 01:04:57,420
Huwa lineari.

1348
01:04:57,420 --> 01:04:59,600
>> U inħoss bħal dan huwa tip ta 'stupid.

1349
01:04:59,600 --> 01:05:02,890
Jekk il-persuna li jmiss fil-linja huwa li jmiss
persuna li suppost li jmorru fil-

1350
01:05:02,890 --> 01:05:04,660
maħżen, dawn mhux kollha għandhom
li jiċċaqalqu flimkien.

1351
01:05:04,660 --> 01:05:08,200
Just let tali persuna tiġi mnittfa off
meta jasal iż-żmien, per eżempju.

1352
01:05:08,200 --> 01:05:09,870
Allura aħna tista 'tiffranka ftit ta' żmien hemmhekk.

1353
01:05:09,870 --> 01:05:14,840
U hekk li tagħmel dan għalkemm, li l-mezzi
li l-kap tal-kju jew il-

1354
01:05:14,840 --> 01:05:18,060
quddiem tal-kju se
timxi progressivament aktar profonda u aktar profonda

1355
01:05:18,060 --> 01:05:23,340
fil-firxa u eventwalment tista '
attwalment perimetrika jekk aħna qed jużaw

1356
01:05:23,340 --> 01:05:25,790
array biex jaħżnu l-poplu
f'dan kju.

1357
01:05:25,790 --> 01:05:28,390
Allura inti tista 'kważi think tal-
array bħala data ċirkolari

1358
01:05:28,390 --> 01:05:29,880
istruttura f'dan is-sens.

1359
01:05:29,880 --> 01:05:33,970
>> Allura inti b'xi għandhom iżommu rekord ta 'l-
daqs ta 'dan jew verament l-aħħar ta' dan

1360
01:05:33,970 --> 01:05:36,250
u mbagħad meta l-bidu ta 'dan huwa.

1361
01:05:36,250 --> 01:05:39,490
Allura aħna nipproponu li inti tiddikjara
kju waħda tali, li ssejjaħ

1362
01:05:39,490 --> 01:05:41,330
it q, biss ittra waħda.

1363
01:05:41,330 --> 01:05:44,570
Imbagħad aħna nipproponu li l-front jkun
initialized għal żero u li d-daqs

1364
01:05:44,570 --> 01:05:45,470
jiġu initialized għal żero.

1365
01:05:45,470 --> 01:05:47,770
>> Allura issa dritt, m'hemm xejn
ġewwa ta 'dak kju.

1366
01:05:47,770 --> 01:05:50,910
U aħna nitolbuk biex jitlesta l-
implimentazzjoni ta 'enqueue hawn taħt fil

1367
01:05:50,910 --> 01:05:55,250
b'tali mod li l-funzjoni żżid n biex
l-aħħar ta 'q u mbagħad jirritornaha vera.

1368
01:05:55,250 --> 01:05:58,690
Imma jekk q hija sħiħa jew negattiva, il-
funzjoni għandha minflok jirritornaw falza.

1369
01:05:58,690 --> 01:06:01,060
U aħna ħadt koppja
ta 'suppożizzjonijiet.

1370
01:06:01,060 --> 01:06:04,320
Iżda dawn mhux qed verament funzjonalment
rilevanti, biss li bool jeżisti,

1371
01:06:04,320 --> 01:06:06,690
għaliex, teknikament, bool ma
jeżistu C sakemm inti jinkludu

1372
01:06:06,690 --> 01:06:07,310
ċerti fajl header.

1373
01:06:07,310 --> 01:06:09,350
Allura li kien biss tagħmel ċert li jkun hemm
kinux dan huwa trick

1374
01:06:09,350 --> 01:06:10,940
kwistjoni tip ta 'ħaġa.

1375
01:06:10,940 --> 01:06:16,280
>> Allura enqueue, aħna propost fil-kampjun
soluzzjonijiet biex jimplimentaw kif ġej.

1376
01:06:16,280 --> 01:06:20,420
Waħda, aħna l-ewwel jivverifika l-faċilità,
l-frott jiddendlu baxx.

1377
01:06:20,420 --> 01:06:23,820
Jekk il-kju hija sħiħa jew in-numru li
int tipprova li daħħal hija anqas

1378
01:06:23,820 --> 01:06:26,380
minn żero, li għidna fil-
ispeċifikazzjoni tal-problema għandha

1379
01:06:26,380 --> 01:06:30,320
ma jitħalliex, għaliex aħna biss trid
Valuri mhux negattivi, imbagħad inti għandek

1380
01:06:30,320 --> 01:06:31,640
biss ritorn foloz immedjatament.

1381
01:06:31,640 --> 01:06:33,820
Allura xi relattivament faċli
verifika żball.

1382
01:06:33,820 --> 01:06:38,720
Jekk għalkemm inti tixtieq iżżid li attwali
numru, inti kellha tagħmel daqsxejn ta '

1383
01:06:38,720 --> 01:06:39,440
ħsieb hawnhekk.

1384
01:06:39,440 --> 01:06:41,330
U dan huwa fejn huwa ftit annoying
mentalment, peress li inti għandek

1385
01:06:41,330 --> 01:06:43,000
figura kif jimmaniġġjaw trembil.

1386
01:06:43,000 --> 01:06:46,870
>> Iżda l-raħs tal-idea hawnhekk li l-ta
interess lilna huwa li trembil

1387
01:06:46,870 --> 01:06:51,480
spiss jimplika aritmetika modulari u
l-operatur mod, il-ġenb fil-mija,

1388
01:06:51,480 --> 01:06:55,140
fejn inti tista 'tmur minn valur ikbar
lura għal żero u mbagħad wieħed u tnejn u

1389
01:06:55,140 --> 01:06:58,650
tlieta u mbagħad lura madwar għal żero,
wieħed u tnejn u tlieta u oħrajn

1390
01:06:58,650 --> 01:06:59,380
ġdid u għal darb'oħra.

1391
01:06:59,380 --> 01:07:02,880
Allura l-mod kif qed nipproponu isir dan huwa
li rridu nagħmlu għall-indiċi fil-

1392
01:07:02,880 --> 01:07:05,850
array ċemplu numri fejn
interi tagħna jinsabu.

1393
01:07:05,850 --> 01:07:10,740
Iżda biex naslu s'hemm, aħna l-ewwel trid tagħmel
x'ikun id-daqs tal-kju, iżda huwa

1394
01:07:10,740 --> 01:07:14,080
imbagħad żid li tkun xi tkun l-
quddiem il-lista hija.

1395
01:07:14,080 --> 01:07:17,880
U l-effett ta 'dan huwa li tpoġġi us fi
il-pożizzjoni dritt fil-kju u

1396
01:07:17,880 --> 01:07:20,970
Ma jassumu li l-ewwel persuna fil-linja
huwa fil-bidu, li hu jew

1397
01:07:20,970 --> 01:07:24,130
hi assolutament tista 'tkun jekk aħna
kienu ċaqliq wkoll kulħadd.

1398
01:07:24,130 --> 01:07:26,710
Iżda aħna qed biss ħolqien tax-xogħol
għalina jekk aħna ħa

1399
01:07:26,710 --> 01:07:27,800
dik it-triq partikolari.

1400
01:07:27,800 --> 01:07:29,330
>> Allura nistgħu jżommha relattivament sempliċi.

1401
01:07:29,330 --> 01:07:32,180
We do niftakru li aħna biss
żiedet int mal-kju.

1402
01:07:32,180 --> 01:07:35,850
U allura aħna biss jirritornaw veru.

1403
01:07:35,850 --> 01:07:38,560
Sadanittant, fl dequeue, staqsejna
inti tagħmel dan li ġej.

1404
01:07:38,560 --> 01:07:42,260
Jimplimentawha b'tali mod li
dequeues, li hija tneħħi u prospetti,

1405
01:07:42,260 --> 01:07:44,190
l-int fuq quddiem tal-kju.

1406
01:07:44,190 --> 01:07:46,410
Biex tneħħi l-int, huwa biżżejjed
biex tinsa dan.

1407
01:07:46,410 --> 01:07:47,650
Inti ma għandekx bżonn li jiskarta daqsxejn tagħha.

1408
01:07:47,650 --> 01:07:48,820
Allura huwa għadu attwalment hemm.

1409
01:07:48,820 --> 01:07:51,930
Eżatt bħal data dwar hard drive,
aħna qed biss jinjora l-fatt

1410
01:07:51,930 --> 01:07:52,970
li huwa issa hemmhekk.

1411
01:07:52,970 --> 01:07:55,520
U jekk q hija vojta, għandna
minflok jirritornaw negattiv 1.

1412
01:07:55,520 --> 01:07:56,750
Allura dan iħoss arbitrarja.

1413
01:07:56,750 --> 01:08:01,640
Għaliex ritorn negattiv 1
minflok falza?

1414
01:08:01,640 --> 01:08:02,620
Yeah.

1415
01:08:02,620 --> 01:08:05,070
>> UDJENZA: Q hija l-ħażna
valuri pożittivi.

1416
01:08:05,070 --> 01:08:10,950
Peress li inti biss żżomm il-valuri pożittivi
fil-q, negattiv huwa żball.

1417
01:08:10,950 --> 01:08:11,510
>> DAVID J. Malan: OK, veru.

1418
01:08:11,510 --> 01:08:14,850
Allura għaliex aħna qed biss ħażna pożittiv
valuri jew żero, allura huwa multa li

1419
01:08:14,850 --> 01:08:18,050
ritorn valur negattiv bħala sentinella
valur, simbolu speċjali.

1420
01:08:18,050 --> 01:08:21,630
Imma int riskrittura istorja hemmhekk,
minħabba r-raġuni aħna qed biss

1421
01:08:21,630 --> 01:08:25,890
jirritornaw valuri negattivi mhux
huwa għaliex irridu li

1422
01:08:25,890 --> 01:08:27,670
għandhom valur sentinella.

1423
01:08:27,670 --> 01:08:32,617
Allura aktar speċifiku, għaliex mhux biss
ritorn foloz f'każijiet ta 'żbalji?

1424
01:08:32,617 --> 01:08:33,099
Yeah.

1425
01:08:33,099 --> 01:08:35,510
>> UDJENZA: You ħadthom fallew
li jirritorna numru sħiħ.

1426
01:08:35,510 --> 01:08:36,630
>> DAVID J. Malan: Eżattament.

1427
01:08:36,630 --> 01:08:38,569
U dan huwa fejn C gets
jillimita pretty.

1428
01:08:38,569 --> 01:08:40,590
Jekk inti qed tgħid int ser
li jirritorna l int, inti stajt ltqajna

1429
01:08:40,590 --> 01:08:41,279
li jirritorna l int.

1430
01:08:41,279 --> 01:08:43,689
Inti ma tistax tikseb fancy u jibdew jirritornaw
a bool jew float jew

1431
01:08:43,689 --> 01:08:45,040
string jew xi ħaġa bħal dik.

1432
01:08:45,040 --> 01:08:49,370
Issa, sadanittant, JavaScript u PHP u
xi lingwi oħra jista ', fil-fatt,

1433
01:08:49,370 --> 01:08:51,310
usted jirritornaw differenti
tipi ta 'valuri.

1434
01:08:51,310 --> 01:08:54,819
U li jista 'effettivament tkun utli, fejn
inti tista 'ritorn ints pożittivi, żerijiet,

1435
01:08:54,819 --> 01:08:59,439
ints negattivi, jew falz jew null
anki li turi żball.

1436
01:08:59,439 --> 01:09:01,890
Iżda aħna ma jkollhomx dak
versatilità C.

1437
01:09:01,890 --> 01:09:04,569
>> Allura ma dequeue, dak li aħna
tipproponi li tagħmel huwa -

1438
01:09:04,569 --> 01:09:07,350

1439
01:09:07,350 --> 01:09:09,830
>> ROB BOWDEN: Inti tista 'ritorn foloz.

1440
01:09:09,830 --> 01:09:13,189
Huwa biss li foloz hija hash
jiddefinixxu falza għal żero.

1441
01:09:13,189 --> 01:09:16,000
Mela jekk inti tirritorna falza,
int jirritornaw żero.

1442
01:09:16,000 --> 01:09:25,470
U żero hija ħaġa valida fil-kju tagħna,
billi negattiva 1 mhix jekk

1443
01:09:25,470 --> 01:09:27,000
falza li jkun ġara negattiv 1.

1444
01:09:27,000 --> 01:09:29,972
Imma inti m'għandekx anki
bżonn tkun taf li.

1445
01:09:29,972 --> 01:09:32,399
>> DAVID J. Malan: C'est
għaliex I ma jgħidu li din.

1446
01:09:32,399 --> 01:09:36,450
>> ROB BOWDEN: Iżda dan ma kienx veru
li inti ma jistgħux jirritornaw falza.

1447
01:09:36,450 --> 01:09:37,700
>> DAVID J. Malan: Sure.

1448
01:09:37,700 --> 01:09:40,920

1449
01:09:40,920 --> 01:09:44,240
Allura dequeue, avviż naċċettaw
null bħala argument tagħha.

1450
01:09:44,240 --> 01:09:45,479
U dan għaliex aħna mhux qed
tgħaddi xejn pulzieri

1451
01:09:45,479 --> 01:09:48,359
Aħna biss tixtieq li tneħħi l-element
fuq quddiem tal-kju.

1452
01:09:48,359 --> 01:09:49,819
Allura kif tista we go dwar kif isir dan?

1453
01:09:49,819 --> 01:09:51,290
Ukoll, l-ewwel, ejja tagħmel dan
check sanità malajr.

1454
01:09:51,290 --> 01:09:53,350
Jekk id-daqs kju hija 0, hemm
ebda xogħol li għandu jsir.

1455
01:09:53,350 --> 01:09:54,210
Ritorn negattiv 1.

1456
01:09:54,210 --> 01:09:54,800
Magħmul.

1457
01:09:54,800 --> 01:09:56,340
Allura dak ftit linji tal-programm tiegħi.

1458
01:09:56,340 --> 01:09:58,180
Allura biss erba 'linji jibqgħu.

1459
01:09:58,180 --> 01:10:01,310
>> So here I tiddeċiedi li decrement
id-daqs.

1460
01:10:01,310 --> 01:10:04,620
U decrementing-daqs effettiv
ifisser li jien jinsa

1461
01:10:04,620 --> 01:10:06,010
xi ħaġa fil hemm.

1462
01:10:06,010 --> 01:10:09,910
I iżda wkoll ikollhom jaġġornaw fejn
quddiem tal-numri huma.

1463
01:10:09,910 --> 01:10:11,620
Allura biex tagħmel dan, għandi bżonn
li tagħmel żewġ affarijiet.

1464
01:10:11,620 --> 01:10:16,390
I ewwel jeħtieġ li jiftakru dak in-numru
hija fuq quddiem tal-kju,

1465
01:10:16,390 --> 01:10:17,860
minħabba I bżonn li jirritornaw li ħaġa.

1466
01:10:17,860 --> 01:10:20,910
So I ma tridx aċċidentalment tinsa
dwar dan u mbagħad jissostitwixxu dan.

1467
01:10:20,910 --> 01:10:22,840
Jien biss se tiftakar fi int.

1468
01:10:22,840 --> 01:10:27,310
>> U issa, nixtieq li taġġorna
q.front li jiġu q.front +1.

1469
01:10:27,310 --> 01:10:30,070
Hekk jekk dan kien l-ewwel persuna fil-
linja, issa, I trid tagħmel plus 1

1470
01:10:30,070 --> 01:10:31,930
punt fuq il-persuna li jmiss fil-linja.

1471
01:10:31,930 --> 01:10:33,420
Imma I jkollhom biex jimmaniġġaw dak trembil.

1472
01:10:33,420 --> 01:10:37,270
U jekk il-kapaċità hi kostanti globali,
li għaddej biex jippermettu nagħmel ċert

1473
01:10:37,270 --> 01:10:41,140
kif I punt li l-ħafna aħħar persuna
line, l-operazzjoni modulo se jġib

1474
01:10:41,140 --> 01:10:43,840
me lura għal żero fil-
quddiem tal-kju.

1475
01:10:43,840 --> 01:10:46,050
U li mankijiet-trembil hawn.

1476
01:10:46,050 --> 01:10:48,950
U mbagħad I tipproċedi biex jirritorna n.

1477
01:10:48,950 --> 01:10:51,530
>> Issa, strettament, I ma
jkollha tiddikjara n.

1478
01:10:51,530 --> 01:10:53,880
I ma kellhomx biex grab u jaħżnu
temporanjament, għaliex il-valur huwa

1479
01:10:53,880 --> 01:10:54,740
għadha hemm.

1480
01:10:54,740 --> 01:10:57,490
So I tista 'biss tagħmel l-aritmetika dritt
biex jirritorna l-eks kap

1481
01:10:57,490 --> 01:10:58,450
tal-kju.

1482
01:10:58,450 --> 01:11:01,850
Imma I biss ħassew li dan kien aktar ċar
li attwalment grab l-int, poġġih

1483
01:11:01,850 --> 01:11:04,320
fil-n, u mbagħad jirritornaw li
f'ġieħ iċ-ċarezza iżda

1484
01:11:04,320 --> 01:11:05,735
mhux strettament neċessarju.

1485
01:11:05,735 --> 01:11:09,313

1486
01:11:09,313 --> 01:11:12,130
PSST.

1487
01:11:12,130 --> 01:11:13,410
Huma qed kollha pronunċabbli my head.

1488
01:11:13,410 --> 01:11:15,940

1489
01:11:15,940 --> 01:11:19,110
>> ROB BOWDEN: Allura l-ewwel domanda
hija l-problema siġra binarju.

1490
01:11:19,110 --> 01:11:22,140
Allura l-ewwel kwistjoni hija, aħna qed
minħabba dawn in-numri.

1491
01:11:22,140 --> 01:11:27,160
U rridu li b'xi mod daħħal minnhom fil
dawn in-nodi tali li huwa

1492
01:11:27,160 --> 01:11:30,110
siġra tfittxija binarja valida.

1493
01:11:30,110 --> 01:11:36,260
Allura l-unika ħaġa li tiftakar dwar
siġar tat-tiftix binarju huwa li mhuwiex

1494
01:11:36,260 --> 01:11:39,800
biss li l-ħaġa ix-xellug
huwa inqas u l-ħaġa li

1495
01:11:39,800 --> 01:11:41,120
id-dritt huwa akbar.

1496
01:11:41,120 --> 01:11:44,580
Jeħtieġ li jkun li s-siġra kollu biex
ix-xellug huwa inqas, u l-siġra kollu

1497
01:11:44,580 --> 01:11:45,740
lejn il-lemin huwa akbar.

1498
01:11:45,740 --> 01:11:55,260
>> Mela jekk nressaq 34 hawn fil-quċċata, u mbagħad
Nressaq 20 hawn, b'tali mod li validu hekk

1499
01:11:55,260 --> 01:11:56,970
ferm, għaliex 34 up here.

1500
01:11:56,970 --> 01:11:57,920
20 huwa għaddej ix-xellug.

1501
01:11:57,920 --> 01:11:58,950
Hekk li l-anqas.

1502
01:11:58,950 --> 01:12:03,640
Imma ma nistax mbagħad titqiegħed 59 hawn, għaliex
għalkemm 59 dwar id-dritt ta '20,

1503
01:12:03,640 --> 01:12:06,140
huwa għadu fuq ix-xellug ta '34.

1504
01:12:06,140 --> 01:12:10,760
Allura ma din ir-restrizzjoni fil-moħħ, il-
eħfef mod ta 'probabbilment isolvi din

1505
01:12:10,760 --> 01:12:14,330
problema hija biss tip
ta 'dawn in-numri -

1506
01:12:14,330 --> 01:12:18,720
hekk 20, 34, 36, 52, 59, 106.

1507
01:12:18,720 --> 01:12:21,640
U mbagħad daħħal dawk
mix-xellug għal-lemin.

1508
01:12:21,640 --> 01:12:23,390
>> So 20 tmur hawn.

1509
01:12:23,390 --> 01:12:24,630
34 tmur hawn.

1510
01:12:24,630 --> 01:12:25,830
36 tmur hawn.

1511
01:12:25,830 --> 01:12:29,360
52, 59, 106.

1512
01:12:29,360 --> 01:12:34,730
U inti tista 'wkoll dehret ma
xi ħofor fil u t-twettiq,

1513
01:12:34,730 --> 01:12:38,830
oh, stenna, jien ma jkollhom numri biżżejjed
biex timla dan hawn fuq.

1514
01:12:38,830 --> 01:12:42,170
So I bżonn reshift dak tiegħi
nota rotta se tkun.

1515
01:12:42,170 --> 01:12:47,490
Iżda tinnota li fit-tliet finali, jekk
taqra mix-xellug għal-lemin, huwa fl

1516
01:12:47,490 --> 01:12:48,740
tiżdied ordni.

1517
01:12:48,740 --> 01:12:52,150

1518
01:12:52,150 --> 01:12:56,540
>> Allura issa, irridu li tiddikjara dak il-
Struct se tkun għall-

1519
01:12:56,540 --> 01:12:58,300
punti strateġiċi din is-siġra.

1520
01:12:58,300 --> 01:13:02,720
Allura dak li għandna bżonn fil-siġra binarju?

1521
01:13:02,720 --> 01:13:05,830
Allura aħna jkollhom valur ta 'tip
int, hekk xi valur int.

1522
01:13:05,830 --> 01:13:07,220
I do not know dak li aħna imsejjaħ
fil-soluzzjoni -

1523
01:13:07,220 --> 01:13:08,500
int n.

1524
01:13:08,500 --> 01:13:13,570
Għandna bżonn pointer lill-wild xellug
u pointer lill-wild dritt.

1525
01:13:13,570 --> 01:13:17,540
Allura li għaddej biex teżamina bħal dan.

1526
01:13:17,540 --> 01:13:20,510
U inneħħu fatt tfittex qabel
meta għamlet il-doppjament-linked

1527
01:13:20,510 --> 01:13:25,090
Jittieħed lista, hekk avviż -

1528
01:13:25,090 --> 01:13:27,860
Jien ser ikollhom biex tiskrollja l-
mod lura għal problema 11.

1529
01:13:27,860 --> 01:13:30,980

1530
01:13:30,980 --> 01:13:36,390
>> Allura tinnota li tidher identika għall-dan,
ħlief aħna biss jiġri li jsejħu dawn

1531
01:13:36,390 --> 01:13:38,590
ismijiet differenti.

1532
01:13:38,590 --> 01:13:41,440
Għad għandna integer
valur u żewġ pointers.

1533
01:13:41,440 --> 01:13:44,850
Huwa biss li minflok ta 'trattament l-
pointers dwar tipponta lejn il-ħaġa li jmiss

1534
01:13:44,850 --> 01:13:47,955
u l-ħaġa qabel, aħna qed trattament
l-pointers għall-punt li tifel xellug

1535
01:13:47,955 --> 01:13:49,205
u tfal dritt.

1536
01:13:49,205 --> 01:13:57,372

1537
01:13:57,372 --> 01:13:57,860
OK.

1538
01:13:57,860 --> 01:13:59,650
Allura dak node Struct tagħna.

1539
01:13:59,650 --> 01:14:03,920
U issa, l-unika funzjoni għandna bżonn li
jimplimentaw għal dan hija travers, li

1540
01:14:03,920 --> 01:14:08,320
irridu li jmorru fuq il-siġra, l-istampar
il-valuri tas-siġra fil-ordni.

1541
01:14:08,320 --> 01:14:15,241
>> Allura tfittex hawn, aħna rridu li jistampaw
out 20, 34, 36, 52, 59, u 106.

1542
01:14:15,241 --> 01:14:17,970
Kif nistgħu tlesti dan?

1543
01:14:17,970 --> 01:14:18,890
Allura huwa pjuttost simili.

1544
01:14:18,890 --> 01:14:22,910
Jekk inti raw fil-eżami passat il-problema
li inti ridt li jistampa

1545
01:14:22,910 --> 01:14:25,940
l-siġra sħiħa ma virgoli fl bejn
kollox, kien effettivament anke

1546
01:14:25,940 --> 01:14:27,320
eħfef minn dak.

1547
01:14:27,320 --> 01:14:30,950
Allura hawnhekk huwa s-soluzzjoni.

1548
01:14:30,950 --> 01:14:33,110
Dan kien b'mod sinifikanti aktar faċli
jekk inti ma kien recursively.

1549
01:14:33,110 --> 01:14:36,650
I do not know jekk xi ħadd attentat
biex tagħmel dan iteratively.

1550
01:14:36,650 --> 01:14:38,340
>> Iżda l-ewwel, għandna każ bażi tagħna.

1551
01:14:38,340 --> 01:14:39,660
X'jiġri jekk l-għerq huwa null?

1552
01:14:39,660 --> 01:14:40,610
Imbagħad aħna qed biss ser jirritornaw.

1553
01:14:40,610 --> 01:14:42,300
Aħna ma rridux li jistampaw xejn.

1554
01:14:42,300 --> 01:14:45,940
Else aħna qed tmur biex travers
recursively isfel.

1555
01:14:45,940 --> 01:14:48,140
Stampa l-subtree xellug kollu.

1556
01:14:48,140 --> 01:14:51,440
Allura print kollox inqas
mill-valur kurrenti tiegħi.

1557
01:14:51,440 --> 01:14:53,930
U allura jien ser jistampaw myself.

1558
01:14:53,930 --> 01:14:57,310
U allura jien ser recurse down tiegħi
subtree dritt kollu, hekk kollox

1559
01:14:57,310 --> 01:14:58,810
akbar mill-valur tiegħi.

1560
01:14:58,810 --> 01:15:03,870
U dan se jistampaw
kollox fl-ordni.

1561
01:15:03,870 --> 01:15:05,860
Mistoqsijiet dwar kif dan attwalment
accomplishes dan?

1562
01:15:05,860 --> 01:15:09,892

1563
01:15:09,892 --> 01:15:12,545
>> UDJENZA: Għandi mistoqsija
fuq il-[inaudible].

1564
01:15:12,545 --> 01:15:15,090

1565
01:15:15,090 --> 01:15:23,550
>> ROB BOWDEN: Allura mod wieħed joqrob
kwalunkwe problema rikursivi huwa li jaħsbu biss

1566
01:15:23,550 --> 01:15:26,275
dwar dan simili trid taħseb
dwar il-każijiet kantuniera.

1567
01:15:26,275 --> 01:15:32,150

1568
01:15:32,150 --> 01:15:38,110
Għalhekk tikkunsidra li rridu
Stampa din il-siġra kollu.

1569
01:15:38,110 --> 01:15:42,030
Allura kollha aħna ser tiffoka fuq
huwa dan node partikolari -

1570
01:15:42,030 --> 01:15:43,740
36.

1571
01:15:43,740 --> 01:15:47,420
Is-sejħiet rikursivi, aħna nippretendu
dawk biss xogħol.

1572
01:15:47,420 --> 01:15:54,000
Allura hawn, din is-sejħa rikursivi li
travers, aħna mingħajr ma jaħsbu

1573
01:15:54,000 --> 01:15:58,640
dwar dan, biss jaqsmu ix-xellug
tlieta, jimmaġina li diġà prints 20

1574
01:15:58,640 --> 01:16:00,730
u 34 għalina.

1575
01:16:00,730 --> 01:16:03,350
U mbagħad meta aħna eventwalment recursively
sejħa travers fuq il-

1576
01:16:03,350 --> 01:16:07,890
dritt, li se print korrett
52, 59, u 106 għalina.

1577
01:16:07,890 --> 01:16:13,620
>> Allura peress li dan jista 'jistampa 20, 34, u
l-ieħor jistgħu jistampaw 52, ​​59, 108,

1578
01:16:13,620 --> 01:16:17,180
kollha għandna bżonn li tkun tista 'tagħmel huwa istampar
ourself fin-nofs ta 'dak.

1579
01:16:17,180 --> 01:16:21,250
Allura jistampa kollox quddiemna.

1580
01:16:21,250 --> 01:16:27,710
Stampa ourself, hekk l-istampar node attwali
36, printf regolari, u mbagħad

1581
01:16:27,710 --> 01:16:31,170
print kollox wara us.

1582
01:16:31,170 --> 01:16:32,730
>> DAVID J. Malan: Dan huwa fejn recursion
gets tassew sbieħ.

1583
01:16:32,730 --> 01:16:36,270
Huwa dan qabża aqwa ta 'fidi fejn
inti tagħmel l-tiniest daqsxejn ta 'xogħol.

1584
01:16:36,270 --> 01:16:38,460
U mbagħad inti let xi ħadd
inkella tagħmel l-bqija.

1585
01:16:38,460 --> 01:16:40,180
U li xi ħadd ieħor
hija, ironikament, inti.

1586
01:16:40,180 --> 01:16:44,260

1587
01:16:44,260 --> 01:16:48,360
Allura għal punti brownie serji, jekk
inti iscroll fuq il-mistoqsijiet -

1588
01:16:48,360 --> 01:16:50,530
>> ROB BOWDEN: Fuq id-domandi?

1589
01:16:50,530 --> 01:16:53,490
>> DAVID J. Malan: U jistabbilixxi ftit li
in-numri, ħadd ma jaf fejn

1590
01:16:53,490 --> 01:16:55,190
dawn in-numri jiġu minn?

1591
01:16:55,190 --> 01:16:56,610
>> ROB BOWDEN: I jkollhom litteralment ebda idea.

1592
01:16:56,610 --> 01:16:59,794
>> DAVID J. Malan: Huma jidhru
matul il-kwizz.

1593
01:16:59,794 --> 01:17:01,150
>> UDJENZA: Dawn huma l-istess numri?

1594
01:17:01,150 --> 01:17:01,910
>> DAVID J. Malan: Dawk in-numri.

1595
01:17:01,910 --> 01:17:03,260
A bajd tal-Għid ftit.

1596
01:17:03,260 --> 01:17:08,100
Għalhekk għal dawk minnkom jaraw online fuq
dar, jekk inti tista 'tgħidilna via email

1597
01:17:08,100 --> 01:17:12,680
heads@CS50.net dak is-sinifikat
ta 'dawn is-sitt numri rikorrenti huma

1598
01:17:12,680 --> 01:17:18,560
matul Quiz 1, aħna se doċċa inti
b'attenzjoni aqwa fil-finali

1599
01:17:18,560 --> 01:17:21,610
lecture u ballun stress.

1600
01:17:21,610 --> 01:17:25,460

1601
01:17:25,460 --> 01:17:27,790
Nizza, sottili.

1602
01:17:27,790 --> 01:17:29,570
>> ROB Bowden: Kwalunkwe mistoqsijiet aħħar
dwar xi ħaġa fuq l-kwizz?

1603
01:17:29,570 --> 01:17:32,608