1
00:00:00,000 --> 00:00:00,500

2
00:00:00,500 --> 00:00:11,137
[Daqq ta mużika]

3
00:00:11,137 --> 00:00:12,220
DAVID J. Malan: Kull dritt.

4
00:00:12,220 --> 00:00:13,950
Dan huwa CS50.

5
00:00:13,950 --> 00:00:18,560
Dan huwa ħamsa ġimgħa kontinwa, u aħna
għandhom xi aħbar tajba u xi aħbar ħażina.

6
00:00:18,560 --> 00:00:21,140
Allura aħbar tajba hija li CS50
tniedi dan Ġimgħa.

7
00:00:21,140 --> 00:00:24,430
Jekk inti tixtieq li jingħaqdu magħna,
ras għall-URL tas-soltu hawn.

8
00:00:24,430 --> 00:00:28,670
Aħbarijiet anki aħjar, ebda lecture
dan ġejjin it-tnejn l-13.

9
00:00:28,670 --> 00:00:31,970
Ftit inqas aħbarijiet aħjar,
kwizz żero hija l-Erbgħa li jmiss.

10
00:00:31,970 --> 00:00:33,840
Aktar dettalji jistgħu jkunu
tinstab fuq dan il-URL hawn.

11
00:00:33,840 --> 00:00:36,340
U matul il-jiem koppja li jmiss
aħna ser tkun timla l-vojt

12
00:00:36,340 --> 00:00:39,234
fir-rigward l-kmamar
li aħna se jkunu riżervati.

13
00:00:39,234 --> 00:00:41,400
Aħbarijiet Aħjar hija li hemm ser
tkun reviżjoni kors wiesgħa

14
00:00:41,400 --> 00:00:43,570
sessjoni din ġejjin
It-tnejn fil-għaxija.

15
00:00:43,570 --> 00:00:46,270
Soġġorn sintonizzat għall-tal-kors
websajt għal post u dettalji.

16
00:00:46,270 --> 00:00:49,290
Taqsimiet, anki jekk huwa
vaganzi, se jiltaqa 'wkoll ukoll.

17
00:00:49,290 --> 00:00:50,490

18
00:00:50,490 --> 00:00:52,940
Best aħbarijiet, lecture il-ġimgħa d-dieħla.

19
00:00:52,940 --> 00:00:56,220
Allura dan huwa tradizzjoni aħna
jkollhom, kif fis-sillabu.

20
00:00:56,220 --> 00:00:58,100
Just-- li għaddej biex tkun aqwa.

21
00:00:58,100 --> 00:01:02,510
Inti se tara affarijiet simili
data strutturi ħin kostanti

22
00:01:02,510 --> 00:01:04,730
u tabelli hash u siġar u tipprova.

23
00:01:04,730 --> 00:01:07,150
U aħna ser nitkellmu dwar problemi birthday.

24
00:01:07,150 --> 00:01:09,440
A mazz sħiħ ta 'għalf
jistenna il-ġimgħa li jmiss.

25
00:01:09,440 --> 00:01:11,212

26
00:01:11,212 --> 00:01:12,200
OK.

27
00:01:12,200 --> 00:01:13,190
Xorta.

28
00:01:13,190 --> 00:01:17,080
>> Allura jfakkru li aħna kont qed
jiffoka fuq din l-istampa ta 'x'hemm

29
00:01:17,080 --> 00:01:18,980
ġewwa tal-memorja tal-kompjuter tagħna.

30
00:01:18,980 --> 00:01:22,875
Allura memorja jew RAM huwa fejn programmi
jeżistu waqt li int taħdem magħhom.

31
00:01:22,875 --> 00:01:25,215
Jekk inti double-click
ikona jiddekorri xi program

32
00:01:25,215 --> 00:01:27,520
jew double-click
ikona biex tiftaħ xi fajl,

33
00:01:27,520 --> 00:01:30,430
huwa mgħobbija minn hard tiegħek
issuq jew stat solidu drive

34
00:01:30,430 --> 00:01:34,190
fis RAM, Random Access Memory, fejn
jgħix sakemm il-qawwa imur off,

35
00:01:34,190 --> 00:01:36,700
l-għatu laptop tagħlaq,
jew inti nieqaf-programm.

36
00:01:36,700 --> 00:01:38,960
>> Issa li l-memorja, ta '
li inti probabilment jkollhom

37
00:01:38,960 --> 00:01:41,950
1 gigabyte dawn il-ġranet, 2
gigabytes, jew saħansitra ħafna aktar,

38
00:01:41,950 --> 00:01:44,420
huwa ġeneralment stabbiliti
għal programm partikolari

39
00:01:44,420 --> 00:01:47,170
fil dan it-tip ta 'forma rettangolari
mudell konċettwali

40
00:01:47,170 --> 00:01:50,860
li biha aħna għandna l-munzell fil-qiegħ
u mazz ta 'għalf ieħor fil-quċċata.

41
00:01:50,860 --> 00:01:53,140
Il-ħaġa fil-quċċata ħafna
Rajna fuq din l-istampa

42
00:01:53,140 --> 00:01:55,670
qabel imma qatt ma tkellem dwar
huwa l-hekk imsejħa segment test.

43
00:01:55,670 --> 00:01:58,419
Segment Test huwa biss mod fancy
ta 'tgħid l-żerijiet u dawk li

44
00:01:58,419 --> 00:02:01,150
compose program kkompilata tiegħek attwali.

45
00:02:01,150 --> 00:02:03,910
>> Allura meta inti double-click
Microsoft Word fuq Mac tiegħek jew PC,

46
00:02:03,910 --> 00:02:08,030
jew meta inti tmexxi dot mmejla Mario fuq
Linux kompjuter fid-tieqa terminal tiegħek,

47
00:02:08,030 --> 00:02:12,460
l-żerijiet u dawk li compose
Word jew Mario huma maħżuna temporanjament

48
00:02:12,460 --> 00:02:16,610
fil RAM kompjuter tiegħek fl-hekk imsejħa
segment test għal programm partikolari.

49
00:02:16,610 --> 00:02:19,080
Hawn taħt li tmur initialized
u data uninitialized.

50
00:02:19,080 --> 00:02:22,655
Dan huwa Jittieħed simili varjabbli globali,
li konna mhux użati ħafna,

51
00:02:22,655 --> 00:02:24,910
iżda fuq okkażjoni konna
kellhom varjabbli globali

52
00:02:24,910 --> 00:02:28,819
jew kordi statikament definit li
huwa diffiċli kliem bħal "bonjour" kodifikati

53
00:02:28,819 --> 00:02:31,860
li mhumiex jittieħdu mill-utent
li huma hard-kodifikati fil-programm tiegħek.

54
00:02:31,860 --> 00:02:34,230
>> Issa, stabbiliti fil-qiegħ we
jkollhom l-hekk imsejħa munzell.

55
00:02:34,230 --> 00:02:37,665
U l-munzell, s'issa, aħna kont qed
jużaw għal liema tipi ta 'għanijiet?

56
00:02:37,665 --> 00:02:39,706

57
00:02:39,706 --> 00:02:40,997
X'hemm-munzell ġew użati għall?

58
00:02:40,997 --> 00:02:41,160
Yeah?

59
00:02:41,160 --> 00:02:42,070
>> Udjenza: Funzjonijiet.

60
00:02:42,070 --> 00:02:43,320
>> DAVID J. Malan: Għal funzjonijiet?

61
00:02:43,320 --> 00:02:44,980
F'liema sens għall-funzjonijiet?

62
00:02:44,980 --> 00:02:48,660
>> UDJENZA: Meta inti sejħa funzjoni, il-
l-argumenti huma kkopjati fuq il-munzell.

63
00:02:48,660 --> 00:02:49,660
>> DAVID J. Malan: Eżattament.

64
00:02:49,660 --> 00:02:52,650
Meta inti sejħa funzjoni, tagħha
l-argumenti huma kkopjati fuq il-munzell.

65
00:02:52,650 --> 00:02:56,330
Allura xi X ta jew tal Y jew A jew B tal-
li int tgħaddi ġol funzjoni

66
00:02:56,330 --> 00:02:58,680
huma temporanjament jitqiegħdu fuq
l-hekk imsejħa munzell,

67
00:02:58,680 --> 00:03:02,000
biss bħal wieħed mill-Annenberg
trejs sala dining, u wkoll affarijiet

68
00:03:02,000 --> 00:03:03,190
bħal varjabbli lokali.

69
00:03:03,190 --> 00:03:06,290
Jekk il-funzjoni foo tiegħek jew swap tiegħek
funzjoni jkollhom varjabbli lokali,

70
00:03:06,290 --> 00:03:08,602
bħal temperatura, dawn iż-żewġ
jispiċċaw fuq il-munzell.

71
00:03:08,602 --> 00:03:11,560
Issa, aħna mhux se jitkellmu wisq dwar
minnhom, iżda dawn il-varjabbli ambjent

72
00:03:11,560 --> 00:03:15,690
fil-qiegħ rajna filwaqt li ilu meta
I kien futzing fuq il-keyboard jum wieħed

73
00:03:15,690 --> 00:03:20,050
u bdejt aċċess affarijiet
bħall ARGV 100 jew ARGV 1,000,

74
00:03:20,050 --> 00:03:22,320
biss elements-- ninsa
l numbers-- iżda li

75
00:03:22,320 --> 00:03:24,330
ma kellhomx jiġu aċċessati mill me.

76
00:03:24,330 --> 00:03:26,581
Aħna bdew jaraw xi
simboli funky fuq l-iskrin.

77
00:03:26,581 --> 00:03:28,330
Dawk kienu l-hekk imsejħa
varjabbli ambjent

78
00:03:28,330 --> 00:03:32,390
bħal settings globali għall tiegħi
programm jew għall-kompjuter tiegħi, ma

79
00:03:32,390 --> 00:03:37,090
mhux relatati mal-riċenti
bug li aħna diskussi,

80
00:03:37,090 --> 00:03:39,670
Shellshock, li kien
plaguing pjuttost ftit kompjuters.

81
00:03:39,670 --> 00:03:42,960
>> Issa fl-aħħarnett, fil-fokus tal-lum
aħna ser finalment tkun fuq il-borġ.

82
00:03:42,960 --> 00:03:44,864
Dan huwa chunk ieħor ta 'memorja.

83
00:03:44,864 --> 00:03:47,030
U fundamentalment dan kollu
memorja huwa l-istess għalf.

84
00:03:47,030 --> 00:03:48,040
Hu l-istess ħardwer.

85
00:03:48,040 --> 00:03:49,956
Aħna biss tip ta '
trattament clusters differenti

86
00:03:49,956 --> 00:03:51,460
ta 'bytes għal skopijiet differenti.

87
00:03:51,460 --> 00:03:56,540
Il borġ huwa wkoll se jkun fejn
varjabbli u l-memorja li inti titlob

88
00:03:56,540 --> 00:03:58,810
mis-sistema operattiva
huwa maħżun temporanjament.

89
00:03:58,810 --> 00:04:01,890
>> Iżda hemm tip ta 'problema
hawnhekk, bħala l-istampa jimplika.

90
00:04:01,890 --> 00:04:05,261
Aħna tip ta 'żewġ
vapuri li waslu biex jikkonfliġġu.

91
00:04:05,261 --> 00:04:08,010
Għaliex kif inti tuża aktar u aktar
tal-munzell, u kif naraw llum

92
00:04:08,010 --> 00:04:11,800
onward, kif tuża aktar u aktar ta 'l-
borġ, żgur affarijiet ħżiena jista 'jiġri.

93
00:04:11,800 --> 00:04:15,054
U fil-fatt, nistgħu jinduċu li
intenzjonalment jew mhux intenzjonalment.

94
00:04:15,054 --> 00:04:16,970
Allura l-cliffhanger aħħar
iż-żmien kien dan il-programm,

95
00:04:16,970 --> 00:04:20,570
li ma sservi ebda funzjonali
skop ieħor ħlief li juri

96
00:04:20,570 --> 00:04:24,750
kif inti bħala bad Guy tista 'attwalment tieħu
vantaġġ ta 'bugs fil-programm ta' xi ħadd

97
00:04:24,750 --> 00:04:28,460
u tieħu f'idejha l-programm jew saħansitra
sistema tal-kompjuter sħiħ jew server.

98
00:04:28,460 --> 00:04:31,660
Hekk biss li t'għajn fil-qosor, inti
avviż li prinċipali fil-qiegħ

99
00:04:31,660 --> 00:04:34,510
jieħu fil-kmand linja
argumenti, kif kull ARGV.

100
00:04:34,510 --> 00:04:38,480
U għandu sejħa għal funzjoni f,
essenzjalment funzjoni nameless msejħa

101
00:04:38,480 --> 00:04:40,250
f, u huwa tgħaddi fis-ARGV [1].

102
00:04:40,250 --> 00:04:43,960
>> Allura x'ikun kelma t-tipi utent f'mill
fil-pront wara isem dan il-programm,

103
00:04:43,960 --> 00:04:49,310
u mbagħad din il-funzjoni arbitrarja up
top, f, jieħu fil string, char AKA *,

104
00:04:49,310 --> 00:04:51,720
kif aħna ħadthom bdiet tiddiskuti,
u hija biss jitlob li "bar."

105
00:04:51,720 --> 00:04:53,310
Iżda nistgħu sejħa hija xejn.

106
00:04:53,310 --> 00:04:57,470
U allura jiddikjara, ġewwa
ta f, firxa ta 'karattri

107
00:04:57,470 --> 00:04:59,930
imsejħa c-- 12-il karattru bħal dawn.

108
00:04:59,930 --> 00:05:03,580
>> Issa, mill-istorja I kien javżak
mument ilu, fejn fil-memorja

109
00:05:03,580 --> 00:05:06,720
huwa ċ, jew huma dawk 12
Chars ser jispiċċaw?

110
00:05:06,720 --> 00:05:07,570
Just biex tkun ċara.

111
00:05:07,570 --> 00:05:08,070
Yeah?

112
00:05:08,070 --> 00:05:08,590
>> UDJENZA: Fuq il-munzell.

113
00:05:08,590 --> 00:05:09,420
>> DAVID J. Malan: Fuq il-munzell.

114
00:05:09,420 --> 00:05:10,720
Allura c hija varjabbli lokali.

115
00:05:10,720 --> 00:05:14,079
Aħna qed jitolbu għal 12 Chars jew 12 bytes.

116
00:05:14,079 --> 00:05:16,120
Dawk huma ser jispiċċaw
fuq l-hekk imsejħa munzell.

117
00:05:16,120 --> 00:05:18,530
Issa finalment hija din il-funzjoni l-oħra
li attwalment pretty utli,

118
00:05:18,530 --> 00:05:20,571
imma aħna ħadthom mhux użati verament
dan lilna nfusna, strncopy.

119
00:05:20,571 --> 00:05:21,550

120
00:05:21,550 --> 00:05:25,200
Dan ifisser kopja string, iżda
biss N ittri, n-karattri.

121
00:05:25,200 --> 00:05:31,990
Allura n-karattri se jkunu
kkupjati mill bar fis c.

122
00:05:31,990 --> 00:05:32,980
U kemm?

123
00:05:32,980 --> 00:05:34,110
It-tul ta 'bar.

124
00:05:34,110 --> 00:05:36,330
Allura fi kliem ieħor, li
linja waħda, strncopy,

125
00:05:36,330 --> 00:05:39,500
se kopja
effettiv bar fil sa c.

126
00:05:39,500 --> 00:05:42,340
>> Issa, just biex tip ta jantiċipaw
l-morali ta 'din l-istorja,

127
00:05:42,340 --> 00:05:44,750
dak li huwa potenzjalment problematiku hawn?

128
00:05:44,750 --> 00:05:49,710
Anki jekk aħna qed iċċekkjar t-tul
ta 'bar u li jgħaddi fis strncopy,

129
00:05:49,710 --> 00:05:53,145
dak li hu imsaren tiegħek tghidlek huwa
xorta maqsuma dwar dan il-programm?

130
00:05:53,145 --> 00:05:54,410

131
00:05:54,410 --> 00:05:55,220
Yeah?

132
00:05:55,220 --> 00:05:57,491
>> UDJENZA: Ma tinkludix
spazju għall-karattru null.

133
00:05:57,491 --> 00:05:59,990
DAVID J. Malan: Ma tinkludix
spazju għall-karattru null.

134
00:05:59,990 --> 00:06:02,073
Potenzjalment, b'differenza
prattika tal-passat aħna ma anki

135
00:06:02,073 --> 00:06:04,810
jkollhom daqshekk plus 1 sa
jakkomodaw dan il-karattru null.

136
00:06:04,810 --> 00:06:06,649
Iżda huwa saħansitra agħar minn dik.

137
00:06:06,649 --> 00:06:07,940
X'iktar huma aħna naqset milli tagħmel?

138
00:06:07,940 --> 00:06:08,432
Yeah?

139
00:06:08,432 --> 00:06:09,307
>> UDJENZA: [inaudible]

140
00:06:09,307 --> 00:06:15,440

141
00:06:15,440 --> 00:06:16,440
DAVID J. Malan: Perfect.

142
00:06:16,440 --> 00:06:18,490
Imxejna hard-coded 12 pretty arbitrarju.

143
00:06:18,490 --> 00:06:19,497

144
00:06:19,497 --> 00:06:21,330
Dan mhuwiex tant l-
problema, iżda l-fatt

145
00:06:21,330 --> 00:06:25,630
li aħna mhux qed anki iċċekkjar jekk
it-tul ta 'bar huwa inqas minn 12,

146
00:06:25,630 --> 00:06:28,530
f'liema każ li għaddej biex tkun
sikur biex tqiegħed lilha fil-memorja

147
00:06:28,530 --> 00:06:30,260
imsejħa c li konna allokati.

148
00:06:30,260 --> 00:06:32,960
Tabilħaqq, jekk bar huwa simili
20 karattru twal,

149
00:06:32,960 --> 00:06:39,010
din il-funzjoni tidher li ikkupjar
20 karattri mill bar fis c, u b'hekk

150
00:06:39,010 --> 00:06:41,310
tieħu mill-inqas 8 bytes
li ma għandu jkun.

151
00:06:41,310 --> 00:06:42,690
Dik hija l-implikazzjoni hawnhekk.

152
00:06:42,690 --> 00:06:44,347
>> Għalhekk fil-qosor programm, imkisser.

153
00:06:44,347 --> 00:06:45,180
Mhux tali big deal.

154
00:06:45,180 --> 00:06:46,360
Forsi ikollok tort segmentazzjoni.

155
00:06:46,360 --> 00:06:47,651
Imxejna kollha kellhom bugs fil-programmi.

156
00:06:47,651 --> 00:06:50,196
Aħna lkoll jista 'jkollhom bugs
fi programmi dritt issa.

157
00:06:50,196 --> 00:06:51,320
Imma x'inhu l-implikazzjoni?

158
00:06:51,320 --> 00:06:54,390
Well, Heres verżjoni żżomjati-in ta '
li stampa ta 'memorja tal-kompjuter tiegħi.

159
00:06:54,390 --> 00:06:56,230
Dan huwa l-qiegħ tal munzell tiegħi.

160
00:06:56,230 --> 00:06:59,644
U fil-fatt, fil-qiegħ ħafna huwa x'hemm
imsejħa munzell ta 'rutina ġenitur, mod fancy

161
00:06:59,644 --> 00:07:00,560
ta 'tgħid li l-prinċipali.

162
00:07:00,560 --> 00:07:03,772
Allura li kull min jissejjaħ il-funzjoni
f li aħna qed jitkellem dwar.

163
00:07:03,772 --> 00:07:05,230
Allura dan huwa l-qiegħ tal-munzell.

164
00:07:05,230 --> 00:07:06,640
Indirizz Ritorn hija xi ħaġa ġdida.

165
00:07:06,640 --> 00:07:08,810
Huwa dejjem kien hemm,
dejjem kienet f'dak istampa.

166
00:07:08,810 --> 00:07:10,440
Aħna biss qatt ma imsejħa attenzjoni għalih.

167
00:07:10,440 --> 00:07:15,290
Minħabba jirriżulta l-mod c jaħdem huwa
li meta funzjoni waħda sejħiet ieħor,

168
00:07:15,290 --> 00:07:18,780
mhux biss tagħmel l-argumenti li
funzjoni nikseb imbuttat fuq il-munzell,

169
00:07:18,780 --> 00:07:22,470
mhux biss tagħmel lokali l-funzjoni tal-
varjabbli tikseb imbuttat fuq il-munzell,

170
00:07:22,470 --> 00:07:26,820
xi ħaġa imsejħa indirizz ta 'ritorn
wkoll gets tpoġġi fuq il-munzell.

171
00:07:26,820 --> 00:07:33,330
Speċifikament, jekk sejħiet ewlenin foo, tat ewlenin
indirizz stess fil-memorja, xi ħaġa ox,

172
00:07:33,330 --> 00:07:38,240
effettivament gets tpoġġi fuq il-munzell
b'tali mod li meta f isir eżekuzzjoni tagħha

173
00:07:38,240 --> 00:07:43,630
jaf fejn jaqbżu lura fit-test
segment sabiex ikomplu eżekuzzjoni.

174
00:07:43,630 --> 00:07:47,760
>> Mela jekk aħna qed hawn kunċettwalment,
fil prinċipali, allura f gets imsejħa.

175
00:07:47,760 --> 00:07:50,200
Kif ma f taf min
għall-kontroll idejn lura?

176
00:07:50,200 --> 00:07:52,020
Ukoll, dan ftit
Breadcrumb aħmar hawn,

177
00:07:52,020 --> 00:07:54,978
imsejjaħ il-indirizz ta 'ritorn, hija biss
kontrolli, dak li huwa dak l-indirizz ta 'ritorn?

178
00:07:54,978 --> 00:07:57,039
Oh, let me jaqbżu lura lill prinċipali hawnhekk.

179
00:07:57,039 --> 00:07:59,080
U li ftit
ta oversimplification,

180
00:07:59,080 --> 00:08:00,750
minħabba li l-żerijiet u dawk
għall prinċipali huma teknikament

181
00:08:00,750 --> 00:08:01,967
up hawn fil-segment tech.

182
00:08:01,967 --> 00:08:03,800
Imma dak li l-idea. f
biss irid ikun jaf liema

183
00:08:03,800 --> 00:08:06,680
li fejn il-kontroll finalment tmur lura.

184
00:08:06,680 --> 00:08:09,790
>> Iżda l-mod kompjuters
ilhom stabbiliti affarijiet

185
00:08:09,790 --> 00:08:12,320
bħall varjabbli lokali u
argumenti huwa bħal dan.

186
00:08:12,320 --> 00:08:17,180
Allura fil-quċċata ta 'din l-istampa fil-
blu huwa l-qafas munzell għall f, sabiex kollha

187
00:08:17,180 --> 00:08:19,630
tal-memorja li f
speċifikament qed tuża.

188
00:08:19,630 --> 00:08:22,990
Allura għaldaqstant, avviż li
bar huwa fil din l-istampa.

189
00:08:22,990 --> 00:08:23,980
Bar kien argument tagħha.

190
00:08:23,980 --> 00:08:27,240
U aħna qal li l-argumenti li
funzjonijiet tikseb imbuttat fuq il-munzell.

191
00:08:27,240 --> 00:08:29,910
U c, naturalment, huwa
wkoll fil din l-istampa.

192
00:08:29,910 --> 00:08:33,520
>> U biss għal skopijiet ta 'notazzjoni,
avviż fil-kantuniera tan-naħa tax-xellug

193
00:08:33,520 --> 00:08:37,020
huwa dak li jkun c bracket 0 u
imbagħad ftit isfel lejn il-lemin

194
00:08:37,020 --> 00:08:38,220
huwa ċ bracket 11.

195
00:08:38,220 --> 00:08:41,240
Allura fi kliem ieħor, tista 'timmaġina
li hemm grilja ta 'bytes

196
00:08:41,240 --> 00:08:44,380
hemm, l-ewwel minnhom hija
top xellug, qiegħ tagħha

197
00:08:44,380 --> 00:08:48,360
hija l-aħħar waħda minn dawk 12 bytes.

198
00:08:48,360 --> 00:08:49,930
>> Imma issa jippruvaw fast quddiem.

199
00:08:49,930 --> 00:08:55,580
X'inhu dwar li jiġri jekk aħna jgħaddu
fil-bar string li l-itwal minn c?

200
00:08:55,580 --> 00:08:59,130
U aħna mhux qed iċċekkjar jekk
huwa tabilħaqq aktar minn 12.

201
00:08:59,130 --> 00:09:03,146
Liema parti ta 'din l-istampa se
nikseb miktub fuq ieħor minn bytes 0, 1, 2, 3,

202
00:09:03,146 --> 00:09:07,890
dot dot dot, 11, u mbagħad
bad, 12, 13 sa 19?

203
00:09:07,890 --> 00:09:11,820
X'hemm jiġri hawn,
jekk inti jiddeduċu mill-ordni

204
00:09:11,820 --> 00:09:14,790
li ċ bracket 0 qegħda fil-quċċata
u c bracket 11 huwa tip ta isfel

205
00:09:14,790 --> 00:09:15,812
lejn il-lemin?

206
00:09:15,812 --> 00:09:16,796
Yeah?

207
00:09:16,796 --> 00:09:19,260
>> UDJENZA: Well, li għaddej
li jissostitwixxu l-bar char *.

208
00:09:19,260 --> 00:09:22,260
>> DAVID J. Malan: Yeah, jidher qisu
int ser jissostitwixxu * bar char.

209
00:09:22,260 --> 00:09:26,245
U agħar, jekk inti tibgħat fil verament twila
string, inti tista 'anki jissostitwixxu liema?

210
00:09:26,245 --> 00:09:27,460

211
00:09:27,460 --> 00:09:28,570
L-indirizz ta 'ritorn.

212
00:09:28,570 --> 00:09:31,380
Li għal darb'oħra, huwa biss bħal
Breadcrumb li tgħid il-programm fejn

213
00:09:31,380 --> 00:09:34,060
li jmorru lura meta f
isir qed jissejjaħ.

214
00:09:34,060 --> 00:09:37,140
>> Allura dak guys ħżiena tipikament do
hija jekk dawn jiltaqgħu ma 'programm

215
00:09:37,140 --> 00:09:41,290
li dawn qed kurjuż jekk huwa
sfruttat, Buggy b'tali mod

216
00:09:41,290 --> 00:09:43,550
li hu jew hi jista 'jieħu
vantaġġ ta 'dan bug,

217
00:09:43,550 --> 00:09:45,720
ġeneralment dawn ma jsibux
dan id-dritt l-ewwel darba.

218
00:09:45,720 --> 00:09:48,590
Huma biss tibda tibgħat, per eżempju,
kordi każwali fis-program tiegħek,

219
00:09:48,590 --> 00:09:50,260
jekk fuq il-keyboard,
jew franchement huma probabbilment

220
00:09:50,260 --> 00:09:52,740
jikteb programm ftit li biss
awtomatikament jiġġeneraw kordi,

221
00:09:52,740 --> 00:09:55,430
u jibdew banging fuq il program tiegħek billi
jibgħat fil-lottijiet ta 'inputs differenti

222
00:09:55,430 --> 00:09:56,340
fil tulijiet differenti.

223
00:09:56,340 --> 00:09:58,990
>> Hekk kif crashes programm tiegħek,
li l-ħaġa aqwa.

224
00:09:58,990 --> 00:10:01,020
Għaliex dan ikun ifisser li hu
jew hi skopra

225
00:10:01,020 --> 00:10:02,660
dak li huwa probabbilment tabilħaqq bug.

226
00:10:02,660 --> 00:10:05,830
U allura dawn jistgħu jiksbu aktar għaqlija
u tibda tiffoka b'mod aktar restrittiv

227
00:10:05,830 --> 00:10:07,420
dwar kif jisfruttaw dak bug.

228
00:10:07,420 --> 00:10:11,480
B'mod partikolari, dak li hu jew hi jista '
tagħmel hu li tibgħat, fl-aħjar każ, bonjour.

229
00:10:11,480 --> 00:10:12,210
No big deal.

230
00:10:12,210 --> 00:10:14,750
Huwa string li l-qasir biżżejjed.

231
00:10:14,750 --> 00:10:18,100
Imma x'jiġri jekk hu jew hi jibgħat,
u aħna ser tiġġeneralizza bħala,

232
00:10:18,100 --> 00:10:20,890
attakk code-- hekk żerijiet
u dawk li jagħmlu l-affarijiet

233
00:10:20,890 --> 00:10:25,150
bħal rm-rf, li tneħħi kollox
mill-hard drive jew jibgħat spam

234
00:10:25,150 --> 00:10:27,000
jew b'xi mod tattakka l-magna?

235
00:10:27,000 --> 00:10:29,570
>> Mela jekk kull wieħed minn dawn
ittri A biss tirrappreżenta,

236
00:10:29,570 --> 00:10:32,380
kunċettwalment, attakk, attakk,
attakk, attakk, xi kodiċi bad

237
00:10:32,380 --> 00:10:36,410
li xi ħadd ieħor kiteb, imma
jekk dik il-persuna huwa intelliġenti biżżejjed

238
00:10:36,410 --> 00:10:40,790
li mhux biss jinkludi kollox
għal dawk it-RFS RM, iżda wkoll

239
00:10:40,790 --> 00:10:46,100
jkollhom aħħar ftit bytes tiegħu jew tagħha
jkun hemm numru li jikkorrispondi

240
00:10:46,100 --> 00:10:50,540
fl-indirizz ta 'dmirijietu
jew kodiċi attakk tagħha stess

241
00:10:50,540 --> 00:10:53,820
li hu jew hi mgħoddija fil biss
billi jipprovdulha fil-pront,

242
00:10:53,820 --> 00:10:58,760
inti tista 'effettivament trick l-kompjuter
fis jinnota meta f isir eżekuzzjoni,

243
00:10:58,760 --> 00:11:02,400
oh, wasal iż-żmien għalija biex tiżdied
lura għall-indirizz tar-ritorn aħmar.

244
00:11:02,400 --> 00:11:06,070
Iżda għaliex hu jew hi għandu b'xi mod
jikkoinċidu dak l-indirizz ta 'ritorn

245
00:11:06,070 --> 00:11:09,602
bin-numru tagħhom stess,
u dawn qed intelliġenti biżżejjed

246
00:11:09,602 --> 00:11:11,560
li konfigurati li
numru li jirreferu, kif inti

247
00:11:11,560 --> 00:11:13,740
tara fil-quċċata super
rokna tax-xellug hemm,

248
00:11:13,740 --> 00:11:18,020
l-indirizz attwali fil-tal-kompjuter
memorja ta 'xi wħud mill-kodiċi attakk tagħhom,

249
00:11:18,020 --> 00:11:21,740
Guy ħażina tista trick l-kompjuter
fis eżekuzzjoni kodiċi tiegħu jew tagħha stess.

250
00:11:21,740 --> 00:11:23,700
>> U dan il-kodiċi, għal darb'oħra, jistgħu jiġu xejn.

251
00:11:23,700 --> 00:11:26,120
Huwa ġeneralment sejjaħ
kodiċi qoxra, li huwa biss

252
00:11:26,120 --> 00:11:29,030
mod ta 'tgħid li mhuwiex
ġeneralment xi ħaġa sempliċi bħala rm-rf.

253
00:11:29,030 --> 00:11:32,340
Huwa fil-fatt xi ħaġa simili Bash,
jew programm attwali li tagħtih

254
00:11:32,340 --> 00:11:37,230
jew kontroll programmatiku tagħha biex tesegwixxi
kull ħaġa oħra li jkunu jridu.

255
00:11:37,230 --> 00:11:40,210
Allura fil-qosor, dan kollu
joħroġ mill-fatt sempliċi

256
00:11:40,210 --> 00:11:44,490
li dan bug involut ma iċċekkjar
il-konfini ta 'firxa tiegħek.

257
00:11:44,490 --> 00:11:47,250
U minħabba l-mod
kompjuters xogħol huwa li dawn

258
00:11:47,250 --> 00:11:49,430
jużaw il-munzell minn
b'mod effettiv, kunċettwalment,

259
00:11:49,430 --> 00:11:54,830
qiegħ fuq up, iżda mbagħad l-elementi
timbotta fuq il-munzell jikber top down,

260
00:11:54,830 --> 00:11:56,624
dan huwa oerhört problematiku.

261
00:11:56,624 --> 00:11:58,290
Issa, hemm modi biex jaħdmu madwar dan.

262
00:11:58,290 --> 00:12:00,800
U franchement, hemm lingwi
li biex jaħdmu madwar dan.

263
00:12:00,800 --> 00:12:03,100
Java huwa immuni, per eżempju,
biex din il-kwistjoni partikolari.

264
00:12:03,100 --> 00:12:04,110
Minħabba li ma jagħtuk pointers.

265
00:12:04,110 --> 00:12:05,943
Huma ma jagħtuk
indirizzi memorja diretti.

266
00:12:05,943 --> 00:12:08,560
Allura ma dan il-poter li għandna
tmissx xejn fil-memorja

267
00:12:08,560 --> 00:12:11,580
Irridu taqa, ċertament, ir-riskju kbir.

268
00:12:11,580 --> 00:12:12,430
>> Allura żżomm għajnejk out.

269
00:12:12,430 --> 00:12:14,596
Jekk, franchement, fix-xhur
jew snin li ġejjin, ghaċ

270
00:12:14,596 --> 00:12:17,740
inti taqra dwar xi wħud isfruttament
ta 'programm jew ta' server,

271
00:12:17,740 --> 00:12:22,370
jekk inti qatt tara ħjiel ta 'xi ħaġa
bħal attakk overflow buffer,

272
00:12:22,370 --> 00:12:25,390
jew overflow Munzell huwa tip ieħor
ta 'attakk, simili fl-ispirtu,

273
00:12:25,390 --> 00:12:28,770
kemm tispira l-tal-websajt
isem, jekk tkun taf,

274
00:12:28,770 --> 00:12:33,170
dan kollu jitkellem dwar biss
overflowing-daqs ta 'xi karattru

275
00:12:33,170 --> 00:12:36,200
array jew xi array b'mod aktar ġenerali.

276
00:12:36,200 --> 00:12:38,822
Kwalunkwe mistoqsijiet, allura, fuq dan?

277
00:12:38,822 --> 00:12:39,780
Tippruvax din id-dar.

278
00:12:39,780 --> 00:12:41,620

279
00:12:41,620 --> 00:12:42,300
>> Kull dritt.

280
00:12:42,300 --> 00:12:47,270
Allura malloc s'issa kien ġdida tagħna
ħabib f'dak nistgħu jallokaw memorja

281
00:12:47,270 --> 00:12:50,540
li aħna ma neċessarjament jaf fil
javvanzaw li aħna rridu hekk aħna ma jkollhomx

282
00:12:50,540 --> 00:12:52,920
għall-kodiċi hard fis tagħna
numri programm bħal 12.

283
00:12:52,920 --> 00:12:55,550
Ladarba l-utent jgħidilna kemm
data hu jew hi trid input,

284
00:12:55,550 --> 00:12:58,000
nistgħu malloc li l-memorja ħafna.

285
00:12:58,000 --> 00:13:01,484
>> Allura malloc jirriżulta, għall-
estent konna ilhom jużawha,

286
00:13:01,484 --> 00:13:03,900
espliċitament aħħar darba, u mbagħad
inti guys ilhom jużawha

287
00:13:03,900 --> 00:13:08,160
għall getstring unknowingly għall
diversi ġimgħat, kollha tal-memorja malloc ta

288
00:13:08,160 --> 00:13:09,820
ġej mill-borġ hekk imsejħa.

289
00:13:09,820 --> 00:13:13,852
U dan huwa għaliex getstring, per eżempju,
jistgħu jallokaw memorja dinamiku

290
00:13:13,852 --> 00:13:16,060
mingħajr ma jkunu jafu dak li int
ser tip bil-quddiem,

291
00:13:16,060 --> 00:13:21,520
inti idejn lura pointer għal dak memorja,
u li l-memorja għadu tiegħek li żżomm,

292
00:13:21,520 --> 00:13:24,080
anki wara getstring prospetti.

293
00:13:24,080 --> 00:13:27,450
Minħabba irtirar wara kollox li l-
munzell huwa kontinwament jitla 'u' l isfel,

294
00:13:27,450 --> 00:13:27,950
up u 'l isfel.

295
00:13:27,950 --> 00:13:30,230
U hekk kif din tmur
isfel, li tfisser kull memorja

296
00:13:30,230 --> 00:13:33,030
din il-funzjoni użat għandu
m'għandux jintuża minn ħaddieħor.

297
00:13:33,030 --> 00:13:34,570
Huwa valuri taż-żibel issa.

298
00:13:34,570 --> 00:13:36,120
>> Iżda l-borġ huwa up here.

299
00:13:36,120 --> 00:13:39,360
U x'hemm sbieħ dwar malloc hija li
meta malloc jalloka memorja up here,

300
00:13:39,360 --> 00:13:42,070
mhuwiex impatt, għall-
parti l-kbira, mill-munzell.

301
00:13:42,070 --> 00:13:46,000
U hekk kull funzjoni tista 'aċċess
memorja li ġie malloc'd,

302
00:13:46,000 --> 00:13:49,120
anke permezz ta 'funzjoni bħal getstring,
anki wara hu ritornat.

303
00:13:49,120 --> 00:13:51,700
>> Issa, il-maqlub ta 'malloc huwa b'xejn.

304
00:13:51,700 --> 00:13:53,900
U fil-fatt, ir-regola inti
bżonn biex tibda tadotta

305
00:13:53,900 --> 00:13:58,950
huwa kwalunkwe, kwalunkwe, kwalunkwe ħin li inti tuża malloc
inti trid yourself tuża ħielsa, eventwalment,

306
00:13:58,950 --> 00:14:00,280
fuq dik l-istess pointer.

307
00:14:00,280 --> 00:14:03,289
Dan il-ħin aħna ġew miktub
Buggy, kodiċi buggy, għal ħafna raġunijiet.

308
00:14:03,289 --> 00:14:05,580
Iżda wieħed minnhom kien
tuża l-librerija CS50, li

309
00:14:05,580 --> 00:14:09,010
nnifisha hija deliberatament
Buggy, tnixxijiet memorja.

310
00:14:09,010 --> 00:14:11,410
Kwalunkwe ħin li inti stajt imsejħa getstring
matul l-aħħar ftit ġimgħat

311
00:14:11,410 --> 00:14:13,870
aħna qed tistaqsi l operattiva
sistema, Linux, għall-memorja.

312
00:14:13,870 --> 00:14:15,780
U inti qatt ma ladarba jingħata lura.

313
00:14:15,780 --> 00:14:17,730
U dan mhux, fil-
prattika, ħaġa tajba.

314
00:14:17,730 --> 00:14:20,330
>> U Valgrind, wieħed mill-
għodod introdotti fl Pset 4,

315
00:14:20,330 --> 00:14:22,900
hija kollha dwar tgħin inti
issa jsibu bugs bħal dik.

316
00:14:22,900 --> 00:14:27,060
Iżda grazzi għat-tobba Pset 4 inti m'għandekx bżonn
li tuża l-librerija CS50 jew getstring.

317
00:14:27,060 --> 00:14:31,220
Allura xi bugs relatati mal-memorja huma
finalment se tkun tiegħek stess.

318
00:14:31,220 --> 00:14:34,060
>> Allura malloc hija aktar minn sempliċiment
konvenjenti għal dan il-għan.

319
00:14:34,060 --> 00:14:37,420
Nistgħu attwalment issa ssolvi
problemi fundamentalment differenti,

320
00:14:37,420 --> 00:14:41,640
u fundamentalment isolvu problemi aktar
effettivament bħala kull wegħda ġimgħa żero tal.

321
00:14:41,640 --> 00:14:44,720
S'issa dan huwa l-sexiest
struttura tad-data aħna kellna.

322
00:14:44,720 --> 00:14:47,804
U mill-istruttura tad-data I jfissirx biss
mod ta 'conceptualizing memorja

323
00:14:47,804 --> 00:14:50,720
b'mod li jmur lil hinn minn sempliċiment tgħid,
dan huwa int, dan huwa char.

324
00:14:50,720 --> 00:14:52,930
Nistgħu tibda affarijiet cluster flimkien.

325
00:14:52,930 --> 00:14:54,460
>> Allura firxa dehru qishom dan.

326
00:14:54,460 --> 00:14:57,270
U dak kien importanti f'madwar
array huwa li jagħtik

327
00:14:57,270 --> 00:14:59,724
back-to-back biċċiet ta '
memorja, li kull wieħed minnhom

328
00:14:59,724 --> 00:15:02,765
se tkun tal-istess tip, int,
int, int, int, jew char, char, char,

329
00:15:02,765 --> 00:15:03,330
char.

330
00:15:03,330 --> 00:15:04,496
Iżda hemm ftit negattivi.

331
00:15:04,496 --> 00:15:06,570
Dan per eżempju, huwa
firxa ta 'daqs sitta.

332
00:15:06,570 --> 00:15:10,650
Ejja ngħidu li inti timla dan array b'sitt
numri u mbagħad, għal xi raġuni,

333
00:15:10,650 --> 00:15:13,187
utent tiegħek trid li tagħti
inti-seba 'numru.

334
00:15:13,187 --> 00:15:14,020
Fejn do inti tpoġġi dan?

335
00:15:14,020 --> 00:15:15,490

336
00:15:15,490 --> 00:15:18,990
>> X'hemm-soluzzjoni jekk għandek
ħolqot firxa fuq il-munzell,

337
00:15:18,990 --> 00:15:22,030
per eżempju, biss bil-ġimgħa
tnejn notazzjoni li aħna introdotti,

338
00:15:22,030 --> 00:15:23,730
ta 'parentesi kwadri ma' numru ġewwa?

339
00:15:23,730 --> 00:15:25,160

340
00:15:25,160 --> 00:15:27,260
Well, inti ħadthom ltqajna sitt
numri fil dawn il-kaxxi.

341
00:15:27,260 --> 00:15:28,530
Liema jkun instincts tiegħek tkun?

342
00:15:28,530 --> 00:15:29,973
Fejn kieku inti tixtieq li tqiegħed lilha?

343
00:15:29,973 --> 00:15:30,860
>> UDJENZA: [inaudible]

344
00:15:30,860 --> 00:15:31,315
>> DAVID J. Malan: Jiddispjacini?

345
00:15:31,315 --> 00:15:32,380
>> UDJENZA: Poġġi fuq it-tmiem.

346
00:15:32,380 --> 00:15:33,796
>> DAVID J. Malan: Poġġi fuq it-tmiem.

347
00:15:33,796 --> 00:15:35,880
Hekk biss fuq il-lemin,
barra ta 'din il-kaxxa.

348
00:15:35,880 --> 00:15:38,710
Liema ikun sbieħ, iżda
jinstabx inti ma tistax tagħmel dan.

349
00:15:38,710 --> 00:15:41,350
Għaliex jekk inti ħadthom ma talabx
għal dan blokki ta 'memorja,

350
00:15:41,350 --> 00:15:44,490
jista 'jkun minn koinċidenza li din
qed tintuża minn xi varjabbli oħra

351
00:15:44,490 --> 00:15:45,030
għal kollox.

352
00:15:45,030 --> 00:15:49,210
Think lura ġimgħa jew hekk meta aħna stabbiliti
out ismijiet Zamyla u Davin u Gabe tal

353
00:15:49,210 --> 00:15:49,930
fil-memorja.

354
00:15:49,930 --> 00:15:51,638
Huma kienu litteralment
lura lura lura.

355
00:15:51,638 --> 00:15:53,550
Allura aħna ma tistax neċessarjament
fiduċja li kwalunkwe ta

356
00:15:53,550 --> 00:15:55,800
minn hawn hija disponibbli għall nagħmel użu.

357
00:15:55,800 --> 00:15:56,990
>> Allura x'iktar jista inti tagħmel?

358
00:15:56,990 --> 00:16:00,282
Well, ladarba jirrealizzaw inti
bżonn ta 'firxa ta' daqs seba,

359
00:16:00,282 --> 00:16:02,490
inti tista 'biss toħloq
firxa ta 'daqs seba mbagħad jużaw

360
00:16:02,490 --> 00:16:05,950
a għal loop jew loop waqt,
kopja hija fil-firxa ġdida,

361
00:16:05,950 --> 00:16:09,680
u mbagħad b'xi mod biss jeħles ta '
dan array jew biss tieqaf tuża din.

362
00:16:09,680 --> 00:16:12,130
Iżda li mhux partikolarment effiċjenti.

363
00:16:12,130 --> 00:16:15,340
Fil-qosor, arrays ma let
inti dinamikament resize.

364
00:16:15,340 --> 00:16:17,900
>> Allura fuq naħa waħda ikollok
aċċess bl-addoċċ, li huwa aqwa.

365
00:16:17,900 --> 00:16:20,108
Minħabba li tikri us do affarijiet
bħall firda u conquer,

366
00:16:20,108 --> 00:16:23,100
tfittxija binarja, li kollha konna
tkellem dwar fuq l-iskrin hawn.

367
00:16:23,100 --> 00:16:24,950
Imma inti żebgħa lilek innifsek fis-kantuniera.

368
00:16:24,950 --> 00:16:27,810
Hekk kif inti hit
l-aħħar tal-firxa tiegħek,

369
00:16:27,810 --> 00:16:29,980
inti għandek tagħmel ħafna
operazzjoni għaljin

370
00:16:29,980 --> 00:16:33,910
jew jikteb mazz sħiħ ta 'kodiċi
li issa tittratta dik il-problema.

371
00:16:33,910 --> 00:16:36,680
>> Allura dak li jekk minflok kellna
xi ħaġa imsejħa lista,

372
00:16:36,680 --> 00:16:38,820
jew lista marbuta b'mod partikolari?

373
00:16:38,820 --> 00:16:41,930
X'jiġri jekk minflok li
rettangoli lura lura biex back,

374
00:16:41,930 --> 00:16:45,730
għandna rettangoli li jħallu ftit
daqsxejn ta 'kamra wiggle bejniethom?

375
00:16:45,730 --> 00:16:49,670
U anki jekk stajt miġbuda dan
stampa jew adattati din l-istampa

376
00:16:49,670 --> 00:16:54,696
minn wieħed mit-testi hawn biex tkun lura lejn
lura lura ħafna ordnat, fir-realtà,

377
00:16:54,696 --> 00:16:56,820
wieħed minn dawk rettangoli
jista 'jkun up hawn fil-memorja.

378
00:16:56,820 --> 00:16:58,028
Wieħed minnhom jista 'jkun up here.

379
00:16:58,028 --> 00:17:00,420
Wieħed minnhom jista 'jkun up here,
hawn fuq, u ibqa 'sejjer hekk.

380
00:17:00,420 --> 00:17:02,910
>> Imma dak jekk aħna ġibdet,
f'dan il-każ, vleġeġ

381
00:17:02,910 --> 00:17:05,650
li b'xi mod link dawn
rettangoli flimkien?

382
00:17:05,650 --> 00:17:08,170
Tabilħaqq, Rajna tekniku
Inkarnazzjoni ta vleġġa.

383
00:17:08,170 --> 00:17:09,839

384
00:17:09,839 --> 00:17:13,710
Dak li aħna użati fl-aħħar
jiem li, taħt il-barnuża,

385
00:17:13,710 --> 00:17:15,210
huwa rappreżentattiv ta vleġġa?

386
00:17:15,210 --> 00:17:16,290

387
00:17:16,290 --> 00:17:17,349
A pointer, id-dritt?

388
00:17:17,349 --> 00:17:19,780
>> Allura dak li jekk, minflok
biss ħażna tal-numri,

389
00:17:19,780 --> 00:17:23,130
bħall 9, 17, 22, 26, 34,
dak jekk aħna maħżuna ma

390
00:17:23,130 --> 00:17:27,079
biss numru iżda pointer
li jmiss għal kull tali numru?

391
00:17:27,079 --> 00:17:30,690
Allura li ferm simili inti Thread
labra permezz mazz sħiħ ta 'drapp,

392
00:17:30,690 --> 00:17:32,950
affarijiet b'xi irbit
flimkien, bl-istess mod jista

393
00:17:32,950 --> 00:17:35,550
aħna ma pointers, kif
incarnated mill vleġeġ hawn,

394
00:17:35,550 --> 00:17:38,550
tip ta 'nisġa flimkien
dawn rettangoli individwali

395
00:17:38,550 --> 00:17:41,780
billi effettivament jużaw pointer
li jmiss għal kull numru li

396
00:17:41,780 --> 00:17:46,065
punti li xi numru li jmiss, li
punti li, imbagħad, xi numru li jmiss?

397
00:17:46,065 --> 00:17:47,940
Allura fi kliem ieħor, liema
jekk aħna fil-fatt riedu

398
00:17:47,940 --> 00:17:49,820
biex jimplimentaw xi ħaġa bħal din?

399
00:17:49,820 --> 00:17:53,610
Well sfortunatament, dawn rettangoli,
inqas l-wieħed ma 9, 17, 22,

400
00:17:53,610 --> 00:17:57,040
u ibqa 'sejjer hekk, dawn m'għadhomx
pjazez sbieħ ma 'numri singoli.

401
00:17:57,040 --> 00:17:59,960
Il-qiegħ, rettangolu
hawn taħt 9, per eżempju,

402
00:17:59,960 --> 00:18:04,330
jirrappreżenta dak għandu
tkun pointer, 32 bits.

403
00:18:04,330 --> 00:18:09,460
Issa, jien ma għadhom konxji ta 'kwalunkwe tip ta' dejta
fis-C li jagħtik mhux biss int

404
00:18:09,460 --> 00:18:11,630
iżda pointer kollox.

405
00:18:11,630 --> 00:18:15,020
>> Allura x'inhu l-soluzzjoni jekk irridu
jivvintaw tweġiba tagħna stess għal dan?

406
00:18:15,020 --> 00:18:15,760
Yeah?

407
00:18:15,760 --> 00:18:16,640
>> UDJENZA: [inaudible]

408
00:18:16,640 --> 00:18:17,360
>> DAVID J. Malan: X'hemm li?

409
00:18:17,360 --> 00:18:17,880
>> UDJENZA: Struttura ġdida.

410
00:18:17,880 --> 00:18:19,590
>> DAVID J. Malan: Yeah, hekk għaliex
ma noħolqu struttura ġdida,

411
00:18:19,590 --> 00:18:20,920
jew Ċ, Struct?

412
00:18:20,920 --> 00:18:25,990
Imxejna structs rajna qabel, jekk fil-qosor,
fejn aħna ttrattati bi struttura student

413
00:18:25,990 --> 00:18:27,780
bħal dan, li kellhom l-isem u dar.

414
00:18:27,780 --> 00:18:31,980
Fil Pset 3 tbegħid inti użati kollu
mazz ta 'GRect structs-- u GOvals

415
00:18:31,980 --> 00:18:34,810
li Stanford maħluqa biex
informazzjoni cluster flimkien.

416
00:18:34,810 --> 00:18:38,580
Allura dak li jekk nieħdu din l-istess idea ta '
l-keywords "typedef" u "Struct,"

417
00:18:38,580 --> 00:18:42,890
u mbagħad xi għalf speċifiku student,
u jevolvu dan fil-segwenti:

418
00:18:42,890 --> 00:18:46,210
typedef Struct node-- u node huwa
biss xjenza tal-kompjuter ġeneriku ħafna

419
00:18:46,210 --> 00:18:49,980
tul għal xi ħaġa fi struttura tad-data,
kontenitur fi struttura tad-data.

420
00:18:49,980 --> 00:18:53,900
A node nitlob huwa se jkollu
l n int, totalment sempliċi,

421
00:18:53,900 --> 00:18:58,810
u mbagħad ftit aktar cryptically,
din it-tieni linja, node Struct * jmiss.

422
00:18:58,810 --> 00:19:01,300
Iżda f'termini tekniċi inqas,
dak li huwa dan it-tieni linja

423
00:19:01,300 --> 00:19:02,980
tal-kodiċi ġewwa l-braces kaboċċi?

424
00:19:02,980 --> 00:19:03,737
Yeah?

425
00:19:03,737 --> 00:19:04,851
>> UDJENZA: [inaudible]

426
00:19:04,851 --> 00:19:06,600
DAVID J. Malan: A
pointer li node ieħor.

427
00:19:06,600 --> 00:19:09,910
Allura ċertament, sintattiku ftit cryptic.

428
00:19:09,910 --> 00:19:13,250
Imma jekk inti taqra dan litteralment,
li jmiss huwa l-isem ta 'varjabbli.

429
00:19:13,250 --> 00:19:14,410
X'inhu tip ta 'dejta tagħha?

430
00:19:14,410 --> 00:19:18,206
Huwa verbose ftit dan iż-żmien,
imma hija ta node Struct tip *.

431
00:19:18,206 --> 00:19:22,960
Kwalunkwe ħin Rajna star xi ħaġa, li
ifisser huwa pointer għal dak it-tip data.

432
00:19:22,960 --> 00:19:26,810
Allura li jmiss hija apparentement a
pointer li node Struct.

433
00:19:26,810 --> 00:19:28,310
>> Issa, dak li huwa node Struct?

434
00:19:28,310 --> 00:19:31,044
Well, Avviż inti tara dawk
istess kliem fil kantuniera.

435
00:19:31,044 --> 00:19:33,960
U fil-fatt, inti wkoll tara l-kelma
"Node" stabbiliti hawn fil-qiegħ tax-xellug.

436
00:19:33,960 --> 00:19:35,640
U dan huwa attwalment biss konvenjenza.

437
00:19:35,640 --> 00:19:39,930
Avviż li fid-definizzjoni student tagħna
hemm il-kelma "student" darba biss.

438
00:19:39,930 --> 00:19:42,510
U dan għaliex student
oġġett ma kienx awto-referenzjali.

439
00:19:42,510 --> 00:19:45,340
M'hemm xejn ġewwa ta 'student
li jeħtieġ għall-punt li student ieħor,

440
00:19:45,340 --> 00:19:45,610
persay.

441
00:19:45,610 --> 00:19:47,630
Dan ikun tip ta '
stramb fid-dinja reali.

442
00:19:47,630 --> 00:19:50,880
>> Iżda ma 'node fil marbuta
lista, nagħmlu rridu node

443
00:19:50,880 --> 00:19:53,970
li jkun referenzjali għal oġġett simili.

444
00:19:53,970 --> 00:19:57,900
U hekk avviż-bidla hawnhekk mhix
biss x'hemm ġewwa l-braces kaboċċi.

445
00:19:57,900 --> 00:20:00,800
Iżda aħna żid il-kelma "node"
fil-quċċata kif ukoll

446
00:20:00,800 --> 00:20:02,930
żżidu mal-qiegħ
minflok "student."

447
00:20:02,930 --> 00:20:06,000
U dan huwa biss f'dettalji,
b'tali mod li, għal darb'oħra, l-istruttura tad-data tiegħek

448
00:20:06,000 --> 00:20:11,380
jista 'jkun awto-referenzjali, b'tali mod li
node jista 'jiġbed l node oħra bħal din.

449
00:20:11,380 --> 00:20:13,840
>> Allura dak li huwa dan finalment
ser ifisser għalina?

450
00:20:13,840 --> 00:20:17,560
Ukoll, wieħed, dan il-għalf ġewwa
huwa l-kontenut ta 'node tagħna.

451
00:20:17,560 --> 00:20:19,360
Din ħaġa up here,
kantuniera, huwa biss hekk

452
00:20:19,360 --> 00:20:20,860
li, għal darb'oħra, nistgħu jirreferu għall nfusna.

453
00:20:20,860 --> 00:20:23,401
U allura l-għalf aktar imbiegħda,
anki jekk node huwa terminu ġdid,

454
00:20:23,401 --> 00:20:25,500
forsi, huwa għadu l-
istess bħal student u liema

455
00:20:25,500 --> 00:20:27,520
kien taħt il-barnuża fl SPL.

456
00:20:27,520 --> 00:20:31,095
>> Allura jekk aħna issa riedet tibda
implimentazzjoni ta 'din il-lista marbuta,

457
00:20:31,095 --> 00:20:33,220
kif jista aħna tittraduċi
xi ħaġa bħal din għall-kodiċi?

458
00:20:33,220 --> 00:20:35,350
Well, ejja biss tara
Eżempju ta 'programm li

459
00:20:35,350 --> 00:20:36,840
effettivament juża lista marbuta.

460
00:20:36,840 --> 00:20:40,870
Fost kodiċi tad-distribuzzjoni tal-lum
huwa programm imsejjaħ Lista Zero.

461
00:20:40,870 --> 00:20:44,980
U jekk I run dan I ħolqot super
GUI sempliċi, grafiċi User Interface,

462
00:20:44,980 --> 00:20:46,460
iżda huwa verament ftit printf.

463
00:20:46,460 --> 00:20:50,930
U issa stajt mogħtija lili nnifsi menu ftit
options-- Ħassar, Daħħal, Search,

464
00:20:50,930 --> 00:20:51,750
u travers.

465
00:20:51,750 --> 00:20:52,630
U Nieqaf.

466
00:20:52,630 --> 00:20:55,970
Dawn huma operazzjonijiet biss komuni fuq
struttura tad-data magħrufa bħala lista link.

467
00:20:55,970 --> 00:20:58,409
>> Issa, Ħassar se
jitħassru ċertu numru mil-lista.

468
00:20:58,409 --> 00:21:00,200
Daħħal għaddej biex iżżid
numru għal-lista.

469
00:21:00,200 --> 00:21:02,181
Fittex ser tħares
għall numru fil-lista.

470
00:21:02,181 --> 00:21:04,930
U travers huwa biss mod fancy
ta 'tgħid, walk permezz tal-lista,

471
00:21:04,930 --> 00:21:06,245
ipprintjaha, imma thats it.

472
00:21:06,245 --> 00:21:07,720
Tbiddilx fi kwalunkwe mod.

473
00:21:07,720 --> 00:21:08,570
>> Mela ejja jippruvaw dan.

474
00:21:08,570 --> 00:21:10,160
Ejja imorru quddiem u tat-tip 2.

475
00:21:10,160 --> 00:21:12,710
U mbagħad jien ser
daħħal in-numru, jgħidu 9.

476
00:21:12,710 --> 00:21:13,620
Ikteb.

477
00:21:13,620 --> 00:21:17,480
U issa program tiegħi huwa biss
pprogrammata biex jgħidu, lista issa huwa 9.

478
00:21:17,480 --> 00:21:20,190
Issa, jekk I imorru quddiem u
do Daħħal għal darb'oħra, let

479
00:21:20,190 --> 00:21:23,680
me imorru quddiem u zoom out u tip 17.

480
00:21:23,680 --> 00:21:25,770
Issa lista tiegħi huwa 9, allura 17.

481
00:21:25,770 --> 00:21:27,750
Jekk I do daħħal mill-ġdid, ejja skip wieħed.

482
00:21:27,750 --> 00:21:32,400
Minflok 22, kif kull l-istampa konna
ġew tħares lejn hawnhekk, let me jaqbżu l quddiem

483
00:21:32,400 --> 00:21:34,630
u daħħal 26 li jmiss.

484
00:21:34,630 --> 00:21:36,230
So jien ser tip 26.

485
00:21:36,230 --> 00:21:37,755
Il-lista huwa kif I jistennew.

486
00:21:37,755 --> 00:21:40,630
Imma issa, biss biex tara jekk dan il-kodiċi
se tkun flessibbli, let me issa

487
00:21:40,630 --> 00:21:43,520
tip 22, li mill-inqas
kunċettwalment, jekk aħna qed

488
00:21:43,520 --> 00:21:46,520
Żamma dan magħżula, li huwa tabilħaqq
se tkun gowl ieħor dritt issa,

489
00:21:46,520 --> 00:21:48,690
għandhom imorru fl bejn 17 u 26.

490
00:21:48,690 --> 00:21:50,270
So I hit Ikteb.

491
00:21:50,270 --> 00:21:51,380
Tabilħaqq, li x-xogħlijiet.

492
00:21:51,380 --> 00:21:54,950
U hekk issa let me daħħal il-
aħħar, kull l-istampa, 34.

493
00:21:54,950 --> 00:21:55,450
>> Kull dritt.

494
00:21:55,450 --> 00:21:58,980
Allura għal issa let me jistipulaw li
Ħassar u travers u Search tagħmel,

495
00:21:58,980 --> 00:21:59,760
fil-fatt, ix-xogħol.

496
00:21:59,760 --> 00:22:04,180
Fil-fatt, jekk I do run Fittex, ejja
tfittxija għall-numru 22, Ikteb.

497
00:22:04,180 --> 00:22:05,010
Hija sabet 22.

498
00:22:05,010 --> 00:22:07,580
Allura dan huwa dak li din
programm Lista Zero ma.

499
00:22:07,580 --> 00:22:10,230
>> Imma dak li huwa attwalment għaddejjin
fuq li jimplimenta dan?

500
00:22:10,230 --> 00:22:14,530
Well, l-ewwel I jista 'jkollhom, u tabilħaqq
I do jkollhom, fajl imsejjaħ list0.h.

501
00:22:14,530 --> 00:22:16,540

502
00:22:16,540 --> 00:22:20,690
U x'imkien fil hemm huwa dan
linja, typedef, node Struct,

503
00:22:20,690 --> 00:22:24,850
imbagħad I jkollhom ċingi kaboċċi tiegħi, int n, u
imbagħad struct-- dak li kien id-definizzjoni?

504
00:22:24,850 --> 00:22:26,530

505
00:22:26,530 --> 00:22:28,545
Node Struct jmiss.

506
00:22:28,545 --> 00:22:29,920

507
00:22:29,920 --> 00:22:31,045
Allura għandna bżonn l-istilla.

508
00:22:31,045 --> 00:22:33,420
Issa teknikament we jsibu rwieħhom
l-vizzju tat-tfassil hawnhekk.

509
00:22:33,420 --> 00:22:35,670
Inti tista 'tara kotba u
referenzi online do hemmhekk.

510
00:22:35,670 --> 00:22:36,660
Huwa funzjonalment ekwivalenti.

511
00:22:36,660 --> 00:22:37,980
Fil-fatt, dan huwa xi ftit aktar tipiku.

512
00:22:37,980 --> 00:22:40,563
Imma I ser tkun konsistenti ma 'dak
għamilna aħħar darba u jagħmlu dan.

513
00:22:40,563 --> 00:22:42,350
U mbagħad fl-aħħar, jien ser jagħmlu dan.

514
00:22:42,350 --> 00:22:45,550
>> Allura fil-fajl tal-header
x'imkien, fil list0.h

515
00:22:45,550 --> 00:22:49,200
llum hija din id-definizzjoni Struct,
u forsi xi għalf ieħor.

516
00:22:49,200 --> 00:22:52,580
Sadanittant list0c hemm
ser ikunu ftit affarijiet.

517
00:22:52,580 --> 00:22:54,740
Iżda aħna qed tmur biex ftit
jibdew u mhux jintemm dan.

518
00:22:54,740 --> 00:22:59,690
List0.h huwa fajl irrid
biex jinkludu fil-fajl C tiegħi.

519
00:22:59,690 --> 00:23:03,910
U mbagħad f'xi punt jien
ser ikollhom int, prinċipali, null.

520
00:23:03,910 --> 00:23:06,530
U mbagħad jien ser
għandhom xi to do hawnhekk.

521
00:23:06,530 --> 00:23:10,620
Jien ukoll se jkollhom
prototip, bħal null, tfittxija, int,

522
00:23:10,620 --> 00:23:13,610
n, l-iskop tagħhom fil-ħajja huwa
tiftix għal element.

523
00:23:13,610 --> 00:23:18,310
U mbagħad stabbiliti hawn nitlob fl
kodiċi tal-lum, null, tfittxija, int, n,

524
00:23:18,310 --> 00:23:21,020
ebda virgola iżda braces kaboċċi miftuħa.

525
00:23:21,020 --> 00:23:25,049
U issa I trid tfittex b'xi mod
għal element f'din il-lista.

526
00:23:25,049 --> 00:23:27,340
Iżda aħna ma jkollhomx biżżejjed
informazzjoni fuq l-iskrin għadu.

527
00:23:27,340 --> 00:23:29,800
I jkollhom ma attwalment
irrappreżentata lista nnifisha.

528
00:23:29,800 --> 00:23:33,070
Allura mod wieħed nistgħu jimplimentaw
lista marbuta fi programm

529
00:23:33,070 --> 00:23:37,520
huwa I tip ta 'tixtieq li tagħmel xi ħaġa
bħall tiddikjara marbuta lista up here.

530
00:23:37,520 --> 00:23:40,520
Għas-sempliċità, jien ser jagħmlu
dan globali, anke jekk b'mod ġenerali aħna

531
00:23:40,520 --> 00:23:41,645
m'għandekx tagħmel dan wisq.

532
00:23:41,645 --> 00:23:43,260
Iżda se tissimplifika dan l-eżempju.

533
00:23:43,260 --> 00:23:45,890
So I jridu jiddikjaraw
lista marbuta up here.

534
00:23:45,890 --> 00:23:47,010
Issa, kif jista 'nagħmel dan?

535
00:23:47,010 --> 00:23:48,810

536
00:23:48,810 --> 00:23:50,750
>> Hawn l-istampa ta 'lista marbuta.

537
00:23:50,750 --> 00:23:53,030
U jien ma verament
taf fil-mument kif

538
00:23:53,030 --> 00:23:56,710
Jien ser tmur dwar jirrappreżentaw
tant affarijiet b'sett wieħed biss

539
00:23:56,710 --> 00:23:58,040
varjabbli fil-memorja.

540
00:23:58,040 --> 00:23:59,160
Imma naħseb lura mument.

541
00:23:59,160 --> 00:24:00,830
Dan il-ħin aħna kellna
kordi, li aħna mbagħad

542
00:24:00,830 --> 00:24:02,913
żvelat li jkun arrays ta '
karattri, li aħna mbagħad

543
00:24:02,913 --> 00:24:05,740
żvelat li jkun biss pointer
l-ewwel karattru

544
00:24:05,740 --> 00:24:08,890
fil-firxa ta 'karattri
thats null terminat.

545
00:24:08,890 --> 00:24:13,530
Allura billi li l-loġika, u ma 'dan
stampa tip ta 'jinżera ħsibijiet tiegħek,

546
00:24:13,530 --> 00:24:17,964
dak li għandna attwalment bżonn jiktbu tagħna
kodiċi jirrappreżentaw lista marbuta?

547
00:24:17,964 --> 00:24:21,130
Kemm ta 'din l-informazzjoni għandna bżonn
biex jaqbdu fil-kodiċi C, would you say?

548
00:24:21,130 --> 00:24:22,654

549
00:24:22,654 --> 00:24:23,154
Yeah?

550
00:24:23,154 --> 00:24:24,738
>> UDJENZA: Għandna bżonn pointer għal node.

551
00:24:24,738 --> 00:24:26,237
DAVID J. Malan: A pointer għal node.

552
00:24:26,237 --> 00:24:29,320
B'mod partikolari, liema node kieku tiegħek
instincts jkun li żżomm pointer li?

553
00:24:29,320 --> 00:24:30,026
>> UDJENZA: L-ewwel node.

554
00:24:30,026 --> 00:24:31,942
>> DAVID J. Malan: Yeah,
probabbilment biss l-ewwel.

555
00:24:31,942 --> 00:24:34,030
U avviż, l-ewwel
node hija forma differenti.

556
00:24:34,030 --> 00:24:37,690
Huwa biss nofs id-daqs ta 'l-Struct,
għaliex dan huwa tabilħaqq biss pointer.

557
00:24:37,690 --> 00:24:44,650
Allura dak li inti tista 'tabilħaqq tagħmel huwa jiddikjara
lista marbuta ma jkunu ta 'node tip *.

558
00:24:44,650 --> 00:24:47,780
U ejja biss sejħa hija l-ewwel
u initialize lill null.

559
00:24:47,780 --> 00:24:49,910
Allura null, għal darb'oħra, huwa li ġejjin
fis-istampa hawn.

560
00:24:49,910 --> 00:24:53,620
Mhux biss huwa null użat bħala bħal speċjali
valur tar-ritorn għal affarijiet simili getstring

561
00:24:53,620 --> 00:24:57,770
u malloc, null hija wkoll l-żero
pointer, in-nuqqas ta 'pointer,

562
00:24:57,770 --> 00:24:58,430
jekk inti se.

563
00:24:58,430 --> 00:25:00,309
Dan ifisser biss xejn għadu hawn.

564
00:25:00,309 --> 00:25:02,100
Issa l-ewwel, I jistgħu stajt
sejjaħ dan xejn.

565
00:25:02,100 --> 00:25:04,200
I setgħet hija imsejħa "lista"
jew kwalunkwe numru ta 'affarijiet oħra.

566
00:25:04,200 --> 00:25:06,960
Imma jien ssejjaħ dan "l-ewwel" b'tali mod li
linji it up ma din l-istampa.

567
00:25:06,960 --> 00:25:10,280
Hekk biss bħal string jistax jiġi rappreżentat
bl-indirizz ta 'l-ewwel byte tagħha,

568
00:25:10,280 --> 00:25:11,280
sabiex tista 'lista marbuta.

569
00:25:11,280 --> 00:25:13,480
U aħna ser tara informazzjoni oħra
istrutturi jkunu rappreżentati

570
00:25:13,480 --> 00:25:16,700
b'sett wieħed biss pointer,
vleġġa 32-bit, tipponta

571
00:25:16,700 --> 00:25:18,740
fl-ewwel node fl-istruttura.

572
00:25:18,740 --> 00:25:20,340
>> Imma issa ejja tantiċipa problema.

573
00:25:20,340 --> 00:25:23,230
Jekk jien biss ftakar
fil-programm tiegħi l-indirizz

574
00:25:23,230 --> 00:25:27,220
ta 'l-ewwel node, l-ewwel
rettangolu f'din l-istruttura tad-data,

575
00:25:27,220 --> 00:25:31,760
liema kellhom jkun aħjar il-każ dwar il-
implimentazzjoni tal-bqija tal-lista tiegħi?

576
00:25:31,760 --> 00:25:35,820
X'hemm dettall ewlieni li għaddej
biex tiżgura li dan attwalment xogħlijiet?

577
00:25:35,820 --> 00:25:39,250
U billi "attwalment xogħlijiet" I
mean, ħafna bħal string,

578
00:25:39,250 --> 00:25:42,180
tikri us go mill-ewwel karattru
fl-isem Davin għall-tieni,

579
00:25:42,180 --> 00:25:44,755
għat-tielet, għall-
raba, sa l-aħħar ħafna,

580
00:25:44,755 --> 00:25:47,880
kif nafu meta nkunu fl-aħħar
ta 'lista marbuta li tidher bħal dan?

581
00:25:47,880 --> 00:25:50,035

582
00:25:50,035 --> 00:25:50,660
Meta huwa null.

583
00:25:50,660 --> 00:25:53,640
U stajt rappreżentati dan it-tip ta 'bħala
bħal-jista inġinier elettriku,

584
00:25:53,640 --> 00:25:56,420
mal-ert ftit
simbolu, ta 'tip.

585
00:25:56,420 --> 00:25:58,246
Iżda dan ifisser biss null f'dan il-każ.

586
00:25:58,246 --> 00:26:00,370
Tista 'tiġbed kull numru
ta 'modi, iżda dan awtur

587
00:26:00,370 --> 00:26:02,800
ġara biex jużaw dan is-simbolu hawn.

588
00:26:02,800 --> 00:26:06,260
>> Sakemm aħna qed stringing
kollha ta 'dawn lymph flimkien,

589
00:26:06,260 --> 00:26:08,600
biss ftakar fejn
l-ewwel waħda hija, sakemm

590
00:26:08,600 --> 00:26:11,760
kif aħna tpoġġi simbolu speċjali fil
l-ħafna aħħar node fil-lista,

591
00:26:11,760 --> 00:26:15,130
u aħna ser tuża null, minħabba li l
dak li għandna disponibbli lilna,

592
00:26:15,130 --> 00:26:16,480
din il-lista hija kompluta.

593
00:26:16,480 --> 00:26:20,190
U anki jekk I biss jagħtuk pointer biex
l-ewwel element, inti, il-programmer,

594
00:26:20,190 --> 00:26:22,486
tista 'ċertament aċċess għall-bqija ta' dan.

595
00:26:22,486 --> 00:26:24,360
Imma ejja ejja imħuħ tiegħek
wander ftit,

596
00:26:24,360 --> 00:26:26,140
jekk dawn mhux qed diġà
pjuttost wandered-- x'hemm

597
00:26:26,140 --> 00:26:28,723
se jkun il-ħin qed taħdem ta '
konstatazzjoni xejn f'din il-lista?

598
00:26:28,723 --> 00:26:30,450

599
00:26:30,450 --> 00:26:33,470
Indanna dan, huwa O kbir ta 'n,
li mhix ħażina, fl-ekwità.

600
00:26:33,470 --> 00:26:34,800
Iżda huwa lineari.

601
00:26:34,800 --> 00:26:37,980
Aħna taw up dak karatteristika
ta arrays billi jersqu aktar

602
00:26:37,980 --> 00:26:43,130
lejn din l-istampa ta 'dinamikament
minsuġa flimkien jew lymph marbuta?

603
00:26:43,130 --> 00:26:44,970

604
00:26:44,970 --> 00:26:46,687
Imxejna rrinunzjaw aċċess bl-addoċċ.

605
00:26:46,687 --> 00:26:48,770
Firxa huwa sbieħ għaliex
kollox matematikament

606
00:26:48,770 --> 00:26:50,340
huwa lura lura lura biex lura.

607
00:26:50,340 --> 00:26:52,370
Anke jekk din l-istampa
jistenna pretty, u anki

608
00:26:52,370 --> 00:26:55,830
għalkemm jidher qisu dawn lymph
huma nicely spazjati, fir-realtà

609
00:26:55,830 --> 00:26:56,830
dawn jistgħu jkunu kullimkien.

610
00:26:56,830 --> 00:27:01,590
OX1, Ox50, Ox123, Ox99, dawn
lymph jista 'jkun kullimkien.

611
00:27:01,590 --> 00:27:05,960
Minħabba malloc ma jalloka memorja
mill-munzell, iżda kullimkien fid-borġ.

612
00:27:05,960 --> 00:27:09,080
Inti ma neċessarjament jaf li huwa
se tkun lura lura lura.

613
00:27:09,080 --> 00:27:12,460
U hekk din l-istampa fil-proċess tat-realtà
mhux se jkun pjuttost dan pretty.

614
00:27:12,460 --> 00:27:16,140
>> Allura li għaddej biex jieħu ftit tal-
jaħdmu biex jimplimentaw din il-funzjoni.

615
00:27:16,140 --> 00:27:17,880
Mela ejja jimplimentaw search issa.

616
00:27:17,880 --> 00:27:20,250
U aħna ser tara tip ta '
mod għaqlija ta 'kif isir dan.

617
00:27:20,250 --> 00:27:24,660
Mela jekk I am a funzjoni ta 'tfittxija u
Jien mogħti varjabbli, numru sħiħ n

618
00:27:24,660 --> 00:27:28,490
biex tfittex, I bżonn tkun taf l-
sintassi ġdida għall tfittex ġewwa

619
00:27:28,490 --> 00:27:32,400
ta 'struttura li l-
indikat, biex isibu n.

620
00:27:32,400 --> 00:27:33,210
Mela ejja tagħmel dan.

621
00:27:33,210 --> 00:27:36,030
>> Allura l-ewwel jien se jmorru
quddiem u tiddikjara node *.

622
00:27:36,030 --> 00:27:39,400
U jien ser sejħa hija
pointer, biss billi konvenzjoni.

623
00:27:39,400 --> 00:27:41,710
U jien ser initialize lill-ewwel.

624
00:27:41,710 --> 00:27:43,770
U issa I tista 'tagħmel dan
f'numru ta 'modi.

625
00:27:43,770 --> 00:27:45,436
Imma jien ser tieħu approċċ komuni.

626
00:27:45,436 --> 00:27:50,180
Filwaqt pointer mhuwiex ugwali għal
null, u li l-sintassi validu.

627
00:27:50,180 --> 00:27:54,550
U dan ifisser biss tagħmel dan li ġej, hekk
Sakemm int ma tipponta lejn xejn.

628
00:27:54,550 --> 00:27:55,800
What do I trid tagħmel?

629
00:27:55,800 --> 00:28:01,939
>> Jekk pointer dot n, let me terga 'lura
għal dan, equals-- ugwali liema?

630
00:28:01,939 --> 00:28:03,105
What am I valur tfittex?

631
00:28:03,105 --> 00:28:04,920

632
00:28:04,920 --> 00:28:06,590
Il n attwali li kienet għaddiet.

633
00:28:06,590 --> 00:28:09,020
Allura hawnhekk fattur ieħor
ta 'C u ħafna lingwi.

634
00:28:09,020 --> 00:28:13,705
Anki jekk l-istruttura imsejħa node
għandha n-valur, totalment leġittimu

635
00:28:13,705 --> 00:28:17,530
li jkollu wkoll argument lokali
jew varjabbli imsejħa n.

636
00:28:17,530 --> 00:28:20,085
Minħabba anke aħna, ma '
għajnejn tal-bniedem, jista 'jiddistingwi

637
00:28:20,085 --> 00:28:22,087
li dan huwa n preżumibbilment
differenti minn dan n.

638
00:28:22,087 --> 00:28:23,420
Minħabba li l-sintassi hija differenti.

639
00:28:23,420 --> 00:28:26,211
You ħadthom ltqajna dot u pointer,
billi dan wieħed m'għandu l-ebda ħaġa bħal din.

640
00:28:26,211 --> 00:28:27,290
Allura dan huwa OK.

641
00:28:27,290 --> 00:28:29,120
C'est OK li jsejħu lilhom l-istess affarijiet.

642
00:28:29,120 --> 00:28:32,380
>> Jekk I do inti ssib dan, jien
tmur trid tagħmel xi ħaġa

643
00:28:32,380 --> 00:28:35,000
bħal jħabbar li sibna n.

644
00:28:35,000 --> 00:28:37,930
U aħna ser tħalli li bħala
jikkummenta jew kodiċi pseudocode.

645
00:28:37,930 --> 00:28:40,190
Else, u hawnhekk l-
parti interessanti, liema

646
00:28:40,190 --> 00:28:47,320
do I trid tagħmel jekk il-node attwali
ma fihx n li I care about?

647
00:28:47,320 --> 00:28:50,700
Kif nista jinkiseb dan li ġej?

648
00:28:50,700 --> 00:28:53,710
Jekk finger tiegħi fil-
mument huwa PTR, u huwa

649
00:28:53,710 --> 00:28:55,920
tipponta fi kwalunkwe
ewwel hija li tipponta lejn,

650
00:28:55,920 --> 00:28:59,290
kif nista jimxu finger tiegħi
għall-node li jmiss fil-kodiċi?

651
00:28:59,290 --> 00:29:01,915
Ukoll, x'inhu l-Breadcrumb aħna qed
sejra ssegwi f'dan il-każ?

652
00:29:01,915 --> 00:29:03,464

653
00:29:03,464 --> 00:29:04,380
UDJENZA: [inaudible].

654
00:29:04,380 --> 00:29:05,630
DAVID J. Malan: Yeah, hekk li jmiss.

655
00:29:05,630 --> 00:29:06,640

656
00:29:06,640 --> 00:29:09,824
Mela jekk jien jmorru lura għall tiegħi
kodiċi hawn, tabilħaqq, jien

657
00:29:09,824 --> 00:29:12,990
se jmorru 'l quddiem u jgħidu pointer, li
huwa biss variable-- temporanju huwa

658
00:29:12,990 --> 00:29:15,320
isem stramb, PTR, iżda
huwa biss bħal temp--

659
00:29:15,320 --> 00:29:19,234
Jien ser jistabbilixxu pointer
ugwali għal dak kollu is-- pointer

660
00:29:19,234 --> 00:29:22,150
u għal darb'oħra, dan se jkun
ftit Buggy għal dot moment-- jmiss.

661
00:29:22,150 --> 00:29:23,551

662
00:29:23,551 --> 00:29:26,550
Fi kliem ieħor, jien ser tieħu tiegħi
finger thats tipponta lejn dan node

663
00:29:26,550 --> 00:29:31,247
hawn u jien ser ngħid, inti taf
dak, tagħti ħarsa lejn il-qasam li jmiss

664
00:29:31,247 --> 00:29:33,330
u jimxu saba biex
x'ikun huwa tipponta lejn.

665
00:29:33,330 --> 00:29:35,163
U dan se
irrepeti, irrepeti, irrepeti.

666
00:29:35,163 --> 00:29:37,630
Imma meta ma finger tiegħi
tieqaf tagħmel xejn affattu?

667
00:29:37,630 --> 00:29:40,095
Hekk kif liema linja ta 'kicks kodifika fil?

668
00:29:40,095 --> 00:29:40,970
UDJENZA: [inaudible]

669
00:29:40,970 --> 00:29:43,060
DAVID J. Malan: Jekk il-punt waqt
pointer mhuwiex ugwali għal nulla.

670
00:29:43,060 --> 00:29:44,900
F'xi punt finger tal tiegħi
ser tkun tipponta lejn null

671
00:29:44,900 --> 00:29:47,070
u jien ser tirrealizza
dak l-aħħar ta 'din il-lista.

672
00:29:47,070 --> 00:29:48,910
Issa, dan huwa ftit
jimteddu abjad għas-sempliċità.

673
00:29:48,910 --> 00:29:51,580
Jirriżulta li anke jekk aħna
biss tgħallmu dan dot notazzjoni

674
00:29:51,580 --> 00:29:55,220
għal strutturi, pointer mhix Struct.

675
00:29:55,220 --> 00:29:56,580
PTR huwa dak?

676
00:29:56,580 --> 00:29:58,350
Just biex tkun aktar nitpicky.

677
00:29:58,350 --> 00:29:59,720

678
00:29:59,720 --> 00:30:01,360
Huwa pointer għal node.

679
00:30:01,360 --> 00:30:03,120
Mhuwiex node innifsu.

680
00:30:03,120 --> 00:30:06,650
Jekk I kellu l-ebda stilla hawn, pointer
absolutely-- huwa node.

681
00:30:06,650 --> 00:30:08,650
Dan huwa bħal wieħed ġimgħa
dikjarazzjoni ta 'varjabbli,

682
00:30:08,650 --> 00:30:10,120
anke jekk il-kelma "node" huwa ġdid.

683
00:30:10,120 --> 00:30:13,860
>> Imma hekk kif aħna jintroduċu
star, huwa issa pointer għal node.

684
00:30:13,860 --> 00:30:17,960
U sfortunatament inti ma tistax tuża
l-dot notazzjoni għal pointer.

685
00:30:17,960 --> 00:30:21,070
Int għandek tuża l-vleġġa
notazzjoni, li, impressjonanti,

686
00:30:21,070 --> 00:30:23,470
hija l-ewwel darba xi biċċa
tal sintassi jistenna intuwittivi.

687
00:30:23,470 --> 00:30:25,245
Dan litteralment qisu vleġġa.

688
00:30:25,245 --> 00:30:26,370
U hekk li l-ħaġa tajba.

689
00:30:26,370 --> 00:30:28,995
U 'l isfel hawn litteralment
Dehra vleġġa.

690
00:30:28,995 --> 00:30:31,870
So I think dak l-la-- I ma
think jien over-tikkommetti here-- I

691
00:30:31,870 --> 00:30:34,120
jaħsbu li huwa l-aħħar biċċa ġdida
tal sintassi aħna qed tmur biex tara.

692
00:30:34,120 --> 00:30:36,500
U Thankfully, huwa tabilħaqq
ftit aktar intuwittivi.

693
00:30:36,500 --> 00:30:40,090
>> Issa, għal dawk minnkom li
jista 'jippreferi l-mod qodma,

694
00:30:40,090 --> 00:30:42,550
inti xorta tista 'tuża l-dot notazzjoni.

695
00:30:42,550 --> 00:30:45,380
Imma kif kull nhar it-Tnejn
konverżazzjoni, aħna l-ewwel

696
00:30:45,380 --> 00:30:50,530
bżonn li jmorru hemm, tmur f'dak
jindirizzaw, u mbagħad ikollhom aċċess l-qasam.

697
00:30:50,530 --> 00:30:51,897
Allura dan huwa wkoll korrett.

698
00:30:51,897 --> 00:30:53,730
U franchement, dan huwa
ftit aktar pedantic.

699
00:30:53,730 --> 00:30:56,530
Inti litteralment qal, dereference
l-pointer u jmorru hemm.

700
00:30:56,530 --> 00:30:59,320
Imbagħad grab .n, il-qasam imsejħa n.

701
00:30:59,320 --> 00:31:01,370
Iżda franchement, ebda wieħed irid
tip jew taqra dan.

702
00:31:01,370 --> 00:31:03,620
U hekk id-dinja ivvintat
in-notazzjoni vleġġa, li

703
00:31:03,620 --> 00:31:06,980
hija ekwivalenti, identika,
huwa biss zokkor sintattika.

704
00:31:06,980 --> 00:31:10,570
Allura mod fancy ta 'tgħid dan
jistenna aħjar, jew jistenna aktar sempliċi.

705
00:31:10,570 --> 00:31:12,296
>> Allura issa jien ser tagħmel ħaġa waħda oħra.

706
00:31:12,296 --> 00:31:15,420
Jien se ngħid "break" darba stajt
sabuha so I ma jżommux tfittex għaliha.

707
00:31:15,420 --> 00:31:17,620
Iżda dan huwa l-GIST
ta 'funzjoni ta' tfittxija.

708
00:31:17,620 --> 00:31:21,710
Iżda huwa ħafna aktar faċli, fil-
aħħar, ma jimxu permezz tal-kodiċi.

709
00:31:21,710 --> 00:31:25,570
Dan huwa tabilħaqq l-implimentazzjoni formali
ta 'tfittxija fil-kodiċi ta' distribuzzjoni tal-lum.

710
00:31:25,570 --> 00:31:30,530
I DARE ngħid li daħħal mhix
partikolarment gost li jimxu permezz

711
00:31:30,530 --> 00:31:33,180
viżwalment, u lanqas ma hija tħassar, anke
għalkemm fl-aħħar tal-ġurnata

712
00:31:33,180 --> 00:31:35,460
huma jsarrafx biss fl pjuttost
heuristics sempliċi.

713
00:31:35,460 --> 00:31:36,330
>> Mela ejja tagħmel dan.

714
00:31:36,330 --> 00:31:39,250
Jekk inti ser Humer lili hawn, jien ma
ġġib mazz ta 'blalen istress.

715
00:31:39,250 --> 00:31:40,620
I miġjuba mazz ta 'numri.

716
00:31:40,620 --> 00:31:46,562
U nistgħu tikseb biss ftit voluntiera
biex jirrappreżentaw 9, 17, 20, 22, 29, u 34?

717
00:31:46,562 --> 00:31:48,270
Allura essenzjalment kulħadd
li hawnhekk illum.

718
00:31:48,270 --> 00:31:50,170

719
00:31:50,170 --> 00:31:52,760
Dan kien wieħed, tnejn, tlieta,
erba ', ħames, sitt persuni.

720
00:31:52,760 --> 00:31:55,740
U stajt ġew mitluba biex go-- tara, l-ebda
wieħed fil-dahar tqajjem idejn tagħhom.

721
00:31:55,740 --> 00:32:01,910
OK, wieħed, tnejn, tlieta, erba ',
five-- let me tagħbija balance-- sitta.

722
00:32:01,910 --> 00:32:03,051
OK, inti sitta come fuq up.

723
00:32:03,051 --> 00:32:04,050
Aħna ser bżonn nies oħra.

724
00:32:04,050 --> 00:32:05,460
Aħna miġjuba blalen stress żejjed.

725
00:32:05,460 --> 00:32:08,200
U jekk inti tista ', għall-
ftit mument, linja

726
00:32:08,200 --> 00:32:10,490
yourselves up biss
bħal din l-istampa hawn.

727
00:32:10,490 --> 00:32:15,200

728
00:32:15,200 --> 00:32:15,959
>> Kull dritt.

729
00:32:15,959 --> 00:32:17,125
Ejja naraw, x'hemm isem tiegħek?

730
00:32:17,125 --> 00:32:17,550
>> UDJENZA: Andrew.

731
00:32:17,550 --> 00:32:18,800
>> DAVID J. Malan: Andrew,
inti numru 9.

732
00:32:18,800 --> 00:32:19,540
Nizza li jissodisfaw inti.

733
00:32:19,540 --> 00:32:20,400
Hawnhekk inti tmur.

734
00:32:20,400 --> 00:32:21,593

735
00:32:21,593 --> 00:32:22,176
UDJENZA: Jen.

736
00:32:22,176 --> 00:32:22,662
DAVID J. Malan: Jen.

737
00:32:22,662 --> 00:32:23,162
David.

738
00:32:23,162 --> 00:32:23,765
Numru 17.

739
00:32:23,765 --> 00:32:24,950

740
00:32:24,950 --> 00:32:25,450
Iva?

741
00:32:25,450 --> 00:32:26,400
>> UDJENZA: Jien Julia.

742
00:32:26,400 --> 00:32:26,980
>> DAVID J. Malan: Julia, David.

743
00:32:26,980 --> 00:32:27,545
Numru 20.

744
00:32:27,545 --> 00:32:28,507

745
00:32:28,507 --> 00:32:29,340
UDJENZA: Christian.

746
00:32:29,340 --> 00:32:30,715
DAVID J. Malan: Christian, David.

747
00:32:30,715 --> 00:32:31,541
Numru 22.

748
00:32:31,541 --> 00:32:32,040
U?

749
00:32:32,040 --> 00:32:32,649
>> UDJENZA: JP.

750
00:32:32,649 --> 00:32:33,440
DAVID J. Malan: JP.

751
00:32:33,440 --> 00:32:34,880
Numru 29.

752
00:32:34,880 --> 00:32:37,080
Allura aqbad u jiksbu in-- Uh oh.

753
00:32:37,080 --> 00:32:38,486

754
00:32:38,486 --> 00:32:38,985
Uh oh.

755
00:32:38,985 --> 00:32:39,650

756
00:32:39,650 --> 00:32:40,150
Standby.

757
00:32:40,150 --> 00:32:41,360

758
00:32:41,360 --> 00:32:42,390
20.

759
00:32:42,390 --> 00:32:43,682
Ħadd ma jkollu markatur?

760
00:32:43,682 --> 00:32:44,890
UDJENZA: Stajt ltqajna Sharpie.

761
00:32:44,890 --> 00:32:45,660
DAVID J. Malan: You ltqajna Sharpie?

762
00:32:45,660 --> 00:32:46,159
OK.

763
00:32:46,159 --> 00:32:47,577

764
00:32:47,577 --> 00:32:49,160
U ħadd ma jkollu biċċa karta?

765
00:32:49,160 --> 00:32:51,562

766
00:32:51,562 --> 00:32:52,270
Salv l-lecture.

767
00:32:52,270 --> 00:32:53,810

768
00:32:53,810 --> 00:32:55,362
Come fuq.

769
00:32:55,362 --> 00:32:56,320
UDJENZA: Imxejna ltqajna.

770
00:32:56,320 --> 00:32:57,600
DAVID J. Malan: Aħna ltqajna?

771
00:32:57,600 --> 00:32:58,577
Kull dritt, grazie.

772
00:32:58,577 --> 00:33:01,380

773
00:33:01,380 --> 00:33:02,520
Here we go.

774
00:33:02,520 --> 00:33:03,582
Kien dan mill inti?

775
00:33:03,582 --> 00:33:04,540
Inti biss salvati l-ġurnata.

776
00:33:04,540 --> 00:33:05,670

777
00:33:05,670 --> 00:33:07,220
Allura 29.

778
00:33:07,220 --> 00:33:10,510

779
00:33:10,510 --> 00:33:11,110
Kull dritt.

780
00:33:11,110 --> 00:33:13,360

781
00:33:13,360 --> 00:33:14,890
I misspelled 29, iżda OK.

782
00:33:14,890 --> 00:33:15,720
Jimxi 'l quddiem.

783
00:33:15,720 --> 00:33:18,114
Kull dritt, I ser jagħtuk
pinna tiegħek lura mumentarjament.

784
00:33:18,114 --> 00:33:19,280
Allura aħna għandna dawn folks hawn.

785
00:33:19,280 --> 00:33:20,330
Ejja jkollhom waħda oħra.

786
00:33:20,330 --> 00:33:23,750
Gabe, do inti tixtieq li jkollha
l-ewwel element hawn?

787
00:33:23,750 --> 00:33:25,705
Aħna ser bżonn li inti punt
lejn dawn folks multa.

788
00:33:25,705 --> 00:33:26,930

789
00:33:26,930 --> 00:33:31,030
Allura 9, 17, 20, 22, sort
29, u mbagħad 34.

790
00:33:31,030 --> 00:33:32,160

791
00:33:32,160 --> 00:33:33,325
Did we jitilfu xi ħadd?

792
00:33:33,325 --> 00:33:33,950
I do jkollhom 34.

793
00:33:33,950 --> 00:33:36,730
Fejn did-- OK, li jixtieq li jkun 34?

794
00:33:36,730 --> 00:33:37,605
OK, come fuq up, 34.

795
00:33:37,605 --> 00:33:39,280

796
00:33:39,280 --> 00:33:41,220
Kull dritt, dan se jkun
ukoll jiswa l-quċċata.

797
00:33:41,220 --> 00:33:41,550
X'hemm isem tiegħek?

798
00:33:41,550 --> 00:33:42,040
>> UDJENZA: Peter.

799
00:33:42,040 --> 00:33:43,456
>> DAVID J. Malan: Peter, come fuq up.

800
00:33:43,456 --> 00:33:46,810
Kull dritt, hekk Heres
mazz sħiħ ta 'nodes.

801
00:33:46,810 --> 00:33:49,060
Kull wieħed inti guys jirrappreżenta
waħda minn dawn rettangoli.

802
00:33:49,060 --> 00:33:51,930
U Gabe, il-ftit fard
bniedem out, tirrappreżenta l-ewwel.

803
00:33:51,930 --> 00:33:54,850
Allura pointer tiegħu hija ftit iżgħar
fuq l-iskrin milli kulħadd.

804
00:33:54,850 --> 00:33:58,120
U f'dan il-każ, kull waħda minn tiegħek xellug
idejn se jew punt isfel,

805
00:33:58,120 --> 00:34:01,085
li b'hekk jirrappreżentaw null, hekk
biss l-assenza ta 'pointer,

806
00:34:01,085 --> 00:34:03,210
jew li għaddej biex jiġu tipponta
fi node li jmiss lilek.

807
00:34:03,210 --> 00:34:05,440
>> Allura issa dritt jekk inti adorn
yourselves bħall-istampa

808
00:34:05,440 --> 00:34:07,585
hawn, imorru quddiem u l-punt
fuq xulxin, ma Gabe

809
00:34:07,585 --> 00:34:11,030
b'mod partikolari tipponta lejn
numru 9 li jirrappreżentaw il-lista.

810
00:34:11,030 --> 00:34:14,050
OK, u n-numru 34, naħa tax-xellug tiegħek
għandhom biss jiġu tipponta lejn l-art.

811
00:34:14,050 --> 00:34:15,750
>> OK, għalhekk dan huwa l-lista marbuta.

812
00:34:15,750 --> 00:34:17,580
Allura dan huwa l-xenarju in kwistjoni.

813
00:34:17,580 --> 00:34:20,210
U fil-fatt, dan huwa rappreżentattiv
ta 'klassi ta' problemi

814
00:34:20,210 --> 00:34:21,929
li inti tista 'tipprova biex isolvu bil-kodiċi.

815
00:34:21,929 --> 00:34:25,020
Inti tixtieq li finalment daħħal
element ġdid fil-lista.

816
00:34:25,020 --> 00:34:27,494
F'dan il-każ, aħna qed tmur biex
ipprova ddaħħal in-numru 55.

817
00:34:27,494 --> 00:34:28,500

818
00:34:28,500 --> 00:34:30,860
Iżda hemm għaddej li jkun
każijiet differenti li jikkunsidraw.

819
00:34:30,860 --> 00:34:34,409
U fil-fatt, dan se jkun wieħed
tal-istampa kbar takeaways hawnhekk, hija,

820
00:34:34,409 --> 00:34:35,659
liema huma l-każijiet differenti.

821
00:34:35,659 --> 00:34:39,120
X'inhuma l-kundizzjonijiet differenti jekk jew
fergħat dak il-programm tiegħek jista 'jkollhom?

822
00:34:39,120 --> 00:34:42,024
>> Ukoll, in-numru inti qed tipprova
daħħal, li nafu issa li tkun 55,

823
00:34:42,024 --> 00:34:44,650
imma jekk inti ma taf
bil-quddiem, I daresay

824
00:34:44,650 --> 00:34:47,840
taqa 'mill-inqas tliet
sitwazzjonijiet possibbli.

825
00:34:47,840 --> 00:34:49,717
Fejn jista element ġdid tkun?

826
00:34:49,717 --> 00:34:51,050
UDJENZA: U l-aħħar jew nofs.

827
00:34:51,050 --> 00:34:54,150
DAVID J. Malan: Fl-aħħar, fil-
nofs, jew fil-bidu.

828
00:34:54,150 --> 00:34:56,650
So I jallegaw hemm mill-inqas
tliet problemi għandna bżonn biex isolvu.

829
00:34:56,650 --> 00:34:58,691
Ejja jagħżlu x'hemm forsi
forsi l-aktar sempliċi

830
00:34:58,691 --> 00:35:01,090
wieħed, fejn l-element il-ġdid
tappartjeni fil-bidu.

831
00:35:01,090 --> 00:35:04,040
So jien ser ikollhom kodiċi pjuttost
bħal tiftix, li I biss kiteb.

832
00:35:04,040 --> 00:35:07,670
U jien ser ikollhom PTR, li
I ser jirrappreżentaw hawn ma finger tiegħi,

833
00:35:07,670 --> 00:35:08,370
bħas-soltu.

834
00:35:08,370 --> 00:35:12,430
>> U ftakar, liema valur
aħna ma initialize PTR li?

835
00:35:12,430 --> 00:35:15,300
Allura aħna initialized li nulla inizjalment.

836
00:35:15,300 --> 00:35:16,410

837
00:35:16,410 --> 00:35:19,770
Imma allura dak ma nagħmlu ladarba aħna
kienu ġewwa funzjoni ta 'tfittxija tagħna?

838
00:35:19,770 --> 00:35:20,940

839
00:35:20,940 --> 00:35:24,870
Waqqafna din ugwali għal ewwel,
li ma jfissirx tagħmel dan.

840
00:35:24,870 --> 00:35:25,890

841
00:35:25,890 --> 00:35:30,570
Jekk I sett PTR ugwali għal ewwel, liema
Għandu naħa tiegħi verament tkun tipponta lejn?

842
00:35:30,570 --> 00:35:31,070
Dritt.

843
00:35:31,070 --> 00:35:33,290
Mela jekk Gabe u I huma għaddejjin
li jkun valuri ugwali hawn,

844
00:35:33,290 --> 00:35:34,760
għandna bżonn li kemm punt numru 9.

845
00:35:34,760 --> 00:35:36,420
>> Allura dan kien il-bidu ta 'l-istorja tagħna.

846
00:35:36,420 --> 00:35:38,700
U issa dan huwa biss sempliċi,
anki jekk l-sintassi huwa ġdid.

847
00:35:38,700 --> 00:35:40,580
Kunċettwalment dan huwa biss tfittxija lineari.

848
00:35:40,580 --> 00:35:42,750
Huwa 55 ugwali għal 9?

849
00:35:42,750 --> 00:35:45,559
Jew pjuttost, ejja ngħidu anqas minn 9.

850
00:35:45,559 --> 00:35:47,600
Minħabba jien tipprova
insemmu fejn jitqiegħdu 55.

851
00:35:47,600 --> 00:35:51,270
Inqas minn 9, inqas minn 17, inqas
minn 20, inqas minn 22, inqas minn 29,

852
00:35:51,270 --> 00:35:52,510
inqas minn 34, l-ebda.

853
00:35:52,510 --> 00:35:55,080
Allura issa aħna qed fil-każ
wieħed ta 'mill-inqas tlieta.

854
00:35:55,080 --> 00:35:59,910
>> Jekk irrid daħħal 55 hawn fuq, liema
linji ta 'kodiċi ħtieġa li tikseb esegwiti?

855
00:35:59,910 --> 00:36:01,890
Kif ma din l-istampa ta '
bnedmin bżonn għall-bidla?

856
00:36:01,890 --> 00:36:03,181
What do I do mal-xellug tiegħi?

857
00:36:03,181 --> 00:36:04,530

858
00:36:04,530 --> 00:36:07,360
Dan għandu jkun null inizjalment,
għaliex jien fl-aħħar tal-lista.

859
00:36:07,360 --> 00:36:09,318
U dak li għandu jiġri
hawn ma 'Peter, kien dan?

860
00:36:09,318 --> 00:36:10,520

861
00:36:10,520 --> 00:36:12,430
Hu ovvjament se punt lili.

862
00:36:12,430 --> 00:36:15,580
So I jallegaw hemm mill-inqas żewġ linji
tal-kodiċi fil-kodiċi tal-kampjun mill-lum

863
00:36:15,580 --> 00:36:18,570
li għaddej biex jimplimentaw din
xenarju ta 'żżid 55 fil-denb.

864
00:36:18,570 --> 00:36:20,950
U jista I jkollhom xi ħadd hop
up u biss jirrappreżentaw 55?

865
00:36:20,950 --> 00:36:22,200
Kull dritt, inti l-ġdid 55.

866
00:36:22,200 --> 00:36:23,580

867
00:36:23,580 --> 00:36:27,054
>> Allura issa dak li jekk il-li jmiss
xenarju tidħol flimkien,

868
00:36:27,054 --> 00:36:29,720
u rridu li daħħal fil-
bidu jew il-kap ta 'din il-lista?

869
00:36:29,720 --> 00:36:31,100
U x'hemm isem tiegħek, numru 55?

870
00:36:31,100 --> 00:36:31,420
>> UDJENZA: Jack.

871
00:36:31,420 --> 00:36:32,295
>> DAVID J. Malan: Jack?

872
00:36:32,295 --> 00:36:33,585
OK, sbieħ li jissodisfaw inti.

873
00:36:33,585 --> 00:36:34,210
Merħba abbord.

874
00:36:34,210 --> 00:36:36,640
Allura issa aħna qed tmur biex
daħħal, jiġifieri, in-numru 5.

875
00:36:36,640 --> 00:36:39,840
Hawn il-tieni każ ta 'l-
tlieta aħna ħarāet bil qabel.

876
00:36:39,840 --> 00:36:43,050
Mela jekk 5 jappartjeni fil-bidu,
ejja ara kif insibu li out.

877
00:36:43,050 --> 00:36:46,310
I initialize PTR tiegħi
pointer li numru 9 darb'oħra.

878
00:36:46,310 --> 00:36:49,140
And I realizzati, oh, 5 hija anqas minn 9.

879
00:36:49,140 --> 00:36:50,880
Allura jiffissaw din l-istampa għalina.

880
00:36:50,880 --> 00:36:54,820
Li f'idejha, ​​tal Gabe jew David
or-- x'hemm isem numru 9 tal-?

881
00:36:54,820 --> 00:36:55,740
>> UDJENZA: Jen.

882
00:36:55,740 --> 00:36:58,406
>> DAVID J. Malan: hands-- Jen tal
liema minn idejn tagħna bżonn għall-bidla?

883
00:36:58,406 --> 00:36:58,905

884
00:36:58,905 --> 00:37:00,970
OK, hekk Gabe punti fuq dak li issa?

885
00:37:00,970 --> 00:37:01,640
Fuq me.

886
00:37:01,640 --> 00:37:02,750
I am l-node ġdid.

887
00:37:02,750 --> 00:37:04,870
So I ser biss tip ta 'mossa
hawn biex tara viżwalment.

888
00:37:04,870 --> 00:37:06,435
U sadanittant liema do I punt li?

889
00:37:06,435 --> 00:37:07,910

890
00:37:07,910 --> 00:37:09,020
Still fejn jien tipponta.

891
00:37:09,020 --> 00:37:10,000
Allura thats it.

892
00:37:10,000 --> 00:37:13,717
Hekk biss verament linja waħda ta 'jiffissa kodiċi
din il-kwistjoni partikolari, jidher.

893
00:37:13,717 --> 00:37:14,800
Kull dritt, hekk li tajjeb.

894
00:37:14,800 --> 00:37:17,580
U jista 'xi ħadd tkun placeholder għal 5?

895
00:37:17,580 --> 00:37:18,080
Come fuq up.

896
00:37:18,080 --> 00:37:20,270

897
00:37:20,270 --> 00:37:21,320
Aħna inti ser tingħata ħin li jmiss.

898
00:37:21,320 --> 00:37:24,280
>> Kull dritt, hekk now-- u
Bħala twarrib, l-ismijiet

899
00:37:24,280 --> 00:37:28,510
Jien ma tagħmel referenza espliċita dritt
issa, pointer pred, pointer predeċessur

900
00:37:28,510 --> 00:37:31,260
u pointer ġdida, li l-
biss l-ismijiet mogħtija

901
00:37:31,260 --> 00:37:35,280
fil-kodiċi tal-kampjun għall-pointers jew
idejn tiegħi thats it-tip ta tipponta madwar.

902
00:37:35,280 --> 00:37:36,060
X'hemm isem tiegħek?

903
00:37:36,060 --> 00:37:36,700
>> UDJENZA: Christine.

904
00:37:36,700 --> 00:37:37,100
>> DAVID J. Malan: Christine.

905
00:37:37,100 --> 00:37:38,090
Merħba abbord.

906
00:37:38,090 --> 00:37:42,180
Kull dritt, hekk ejja jikkunsidraw issa
xenarju ftit aktar annoying,

907
00:37:42,180 --> 00:37:46,350
li biha Irrid li daħħal
xi ħaġa bħal 26 fis dan.

908
00:37:46,350 --> 00:37:47,090
20?

909
00:37:47,090 --> 00:37:47,590
What?

910
00:37:47,590 --> 00:37:50,510
Dawn are-- ħaġa tajba li għandna dan pinna.

911
00:37:50,510 --> 00:37:51,955
Kull dritt, 20.

912
00:37:51,955 --> 00:37:53,640

913
00:37:53,640 --> 00:37:57,570
Jekk xi ħadd jistgħu jiksbu ieħor biċċa ta '
karta lesta, biss fil case-- kollha dritt.

914
00:37:57,570 --> 00:37:58,370
Oh, interessanti.

915
00:37:58,370 --> 00:37:59,760

916
00:37:59,760 --> 00:38:02,390
Ukoll dan huwa eżempju
ta 'bug lecture.

917
00:38:02,390 --> 00:38:03,894
OK hekk x'hemm isem tiegħek mill-ġdid?

918
00:38:03,894 --> 00:38:04,560
UDJENZA: Julia.

919
00:38:04,560 --> 00:38:07,559
DAVID J. Malan: Julia, inti tista pop
out u nippretendu inti kienu qatt hemmhekk?

920
00:38:07,559 --> 00:38:09,040
OK, dan qatt ma ġara.

921
00:38:09,040 --> 00:38:09,680
Grazzi.

922
00:38:09,680 --> 00:38:12,180
Allura jissoponi irridu daħħal
Julia fis din il-lista marbuta.

923
00:38:12,180 --> 00:38:13,780
Hija huwa n-numru 20.

924
00:38:13,780 --> 00:38:15,530
U naturalment hi
ser jappartjenu fil-

925
00:38:15,530 --> 00:38:17,521
begin-- ma jurux fil xejn s'issa.

926
00:38:17,521 --> 00:38:20,020
Allura naħa tiegħek jista 'tip ta' jkun
isfel null jew xi valur żibel.

927
00:38:20,020 --> 00:38:21,210
Ejja tgħid l-istorja ta 'malajr.

928
00:38:21,210 --> 00:38:22,980
Jien tipponta lejn numru 5 f'dan il-ħin.

929
00:38:22,980 --> 00:38:23,880
Imbagħad I check 9.

930
00:38:23,880 --> 00:38:25,130
Imbagħad I check 17.

931
00:38:25,130 --> 00:38:26,247
Imbagħad I check 22.

932
00:38:26,247 --> 00:38:27,650

933
00:38:27,650 --> 00:38:32,485
And I realizzata, ooh, Julia
jeħtieġ li tmur qabel it-22.

934
00:38:32,485 --> 00:38:33,580

935
00:38:33,580 --> 00:38:34,660
Allura dak li jeħtieġ li jiġri?

936
00:38:34,660 --> 00:38:35,786

937
00:38:35,786 --> 00:38:36,910
Li f'idejha bżonn għall-bidla?

938
00:38:36,910 --> 00:38:38,360
Tal Julia, mini, or--
x'hemm isem tiegħek mill-ġdid?

939
00:38:38,360 --> 00:38:39,230
>> UDJENZA: Christian.

940
00:38:39,230 --> 00:38:40,060
>> DAVID J. Malan: Christian jew?

941
00:38:40,060 --> 00:38:40,560
>> UDJENZA: Andy.

942
00:38:40,560 --> 00:38:40,905
>> DAVID J. Malan: Andy.

943
00:38:40,905 --> 00:38:41,654
Christian jew Andy?

944
00:38:41,654 --> 00:38:44,280

945
00:38:44,280 --> 00:38:45,690
Andy jeħtieġ li jiġi fi?

946
00:38:45,690 --> 00:38:46,780

947
00:38:46,780 --> 00:38:47,341
Julia.

948
00:38:47,341 --> 00:38:47,840
Kull dritt.

949
00:38:47,840 --> 00:38:48,960
Allura Andy, tridu punt fuq Julia?

950
00:38:48,960 --> 00:38:50,120
Iżda stenna minuta.

951
00:38:50,120 --> 00:38:53,260
Fl-istorja s'issa,
Jien il-tip ta 'wieħed

952
00:38:53,260 --> 00:38:56,800
responsabbli, fis-sens li
pointer huwa l-ħaġa li l-

953
00:38:56,800 --> 00:38:57,850
jiċċaqilqu permezz tal-lista.

954
00:38:57,850 --> 00:39:00,800
Aħna jista 'jkollhom isem għal Andy, iżda
hemm ebda varjabbli imsejħa Andy.

955
00:39:00,800 --> 00:39:04,320
L-unika varjabbli oħra li għandna huwa
ewwel, li s irrappreżentata minn Gabe.

956
00:39:04,320 --> 00:39:07,690
>> Allura dan huwa attwalment għaliex b'hekk
S'issa aħna ve mhux meħtieġ dan.

957
00:39:07,690 --> 00:39:10,846
Imma issa fuq l-iskrin hemm
isemmu għal darb'oħra ta 'pointer pred.

958
00:39:10,846 --> 00:39:11,970
So let me jkun aktar espliċitu.

959
00:39:11,970 --> 00:39:14,820
Jekk dan huwa pointer, kelli aħjar
jiksbu ftit aktar intelliġenti

960
00:39:14,820 --> 00:39:15,950
dwar iterazzjoni tiegħi.

961
00:39:15,950 --> 00:39:19,580
Jekk inti ma mind għaddejjin tiegħi permezz ta 'hawn
darb'oħra, tipponta hawn, tipponta hawn.

962
00:39:19,580 --> 00:39:22,500
Imma let me jkollhom pointer pred,
predeċessur pointer, li l-

963
00:39:22,500 --> 00:39:24,740
tip ta tipponta lejn l-
element I kien biss fil.

964
00:39:24,740 --> 00:39:27,330
Allura meta I go here, issa
aġġornamenti naħa tax-xellug tiegħi.

965
00:39:27,330 --> 00:39:29,370
Meta mmur here aġġornamenti tiegħi tax-xellug.

966
00:39:29,370 --> 00:39:33,090
U issa għandi mhux biss pointer biex
l-element li tmur wara Julia,

967
00:39:33,090 --> 00:39:36,300
I għad għandhom pointer biex
Andy, l-element qabel.

968
00:39:36,300 --> 00:39:39,430
Allura inti għandek aċċess, essenzjalment,
breadcrumbs, jekk inti se,

969
00:39:39,430 --> 00:39:41,500
kollha tal-pointers meħtieġa.

970
00:39:41,500 --> 00:39:43,710
>> Mela jekk jien tipponta lejn
Andy u jien wkoll tipponta

971
00:39:43,710 --> 00:39:47,105
fil Christian, li f'idejha
issa għandu jiġi osservat x'imkien ieħor?

972
00:39:47,105 --> 00:39:48,770

973
00:39:48,770 --> 00:39:51,960
Allura Andy issa jistgħu punt fuq Julia.

974
00:39:51,960 --> 00:39:54,460
Julia issa tista 'punt fuq Christian.

975
00:39:54,460 --> 00:39:56,950
Minħabba li hija tista 'kopja tiegħi
pointer lemin tal.

976
00:39:56,950 --> 00:40:00,044
U li effettivament tpoġġik
lura fis dan il-post hawn.

977
00:40:00,044 --> 00:40:02,460
Għalhekk fil-qosor, anke jekk dan
qed tieħu us tip ta 'dejjem

978
00:40:02,460 --> 00:40:04,510
li attwalment jaġġorna
marbuta lista, tirrealizza

979
00:40:04,510 --> 00:40:06,580
li l-operazzjonijiet
huma relattivament sempliċi.

980
00:40:06,580 --> 00:40:10,030
Huwa ta 'wieħed, tnejn, tlieta
linji ta 'kodiċi finalment.

981
00:40:10,030 --> 00:40:12,780
Iżda imgeżwer madwar dawk
linji ta 'kodiċi preżumibilment

982
00:40:12,780 --> 00:40:16,350
huwa daqsxejn ta 'loġika li effettivament
tqajjem il-mistoqsija, fejn aħna?

983
00:40:16,350 --> 00:40:18,970
Are we fil-bidu,
l-nofs, jew l-aħħar?

984
00:40:18,970 --> 00:40:21,890
>> Issa, hemm ċertament xi oħra
operazzjonijiet nistgħu jimplimentaw.

985
00:40:21,890 --> 00:40:24,880
U dawn l-istampi hawn biss juru
dak li aħna biss għamlet mal-bnedmin.

986
00:40:24,880 --> 00:40:26,080
Xi ngħidu dwar it-tneħħija?

987
00:40:26,080 --> 00:40:30,650
Jekk irrid, per eżempju,
neħħi l-għadd 34 jew 55,

988
00:40:30,650 --> 00:40:34,680
I jista 'jkollhom l-istess tip ta' kodiċi,
imma jien ser bżonn waħda jew żewġ passi.

989
00:40:34,680 --> 00:40:36,110
Minħabba x'hemm ġdid?

990
00:40:36,110 --> 00:40:40,460
Jekk I neħħi xi ħadd fl-aħħar,
bħal numru 55 u mbagħad 34,

991
00:40:40,460 --> 00:40:42,995
dak għandha wkoll tinbidel hekk kif nista 'nagħmlu?

992
00:40:42,995 --> 00:40:44,870
Għandi biex ma evict--
x'hemm isem tiegħek mill-ġdid?

993
00:40:44,870 --> 00:40:45,380
>> UDJENZA: Jack.

994
00:40:45,380 --> 00:40:46,255
>> DAVID J. Malan: Jack.

995
00:40:46,255 --> 00:40:49,770
Għandi biex mhux biss evict-- Jack ħielsa,
hekk litteralment sejħa Jack b'xejn, jew għall-inqas

996
00:40:49,770 --> 00:40:53,530
l-pointer hemmhekk wisq, iżda issa
x'għandu jinbidel ma 'Peter?

997
00:40:53,530 --> 00:40:55,510
Idejn Tiegħu aħjar tibda tipponta 'l isfel.

998
00:40:55,510 --> 00:40:59,300
Għaliex malli I call b'xejn fuq
Jack, jekk Pietru għadu tipponta lejn Jack

999
00:40:59,300 --> 00:41:02,530
u jien għalhekk iżommu traversat
il-lista u l-aċċess dan il-werrej,

1000
00:41:02,530 --> 00:41:05,650
li meta segmentazzjoni tagħna ħabib antik
tort jista 'attwalment kick fil.

1001
00:41:05,650 --> 00:41:07,860
Għaliex aħna ħadthom tingħata l-
memorja lura għall Jack.

1002
00:41:07,860 --> 00:41:10,760
>> Inti tista 'tissospendi hemm
awkwardly għal ftit mument.

1003
00:41:10,760 --> 00:41:13,410
Għaliex għandna biss ftit
operazzjonijiet finali li jikkunsidraw.

1004
00:41:13,410 --> 00:41:15,600
Tneħħi l-kap tal-lista,
jew il-beginning-- u tal dan wieħed

1005
00:41:15,600 --> 00:41:16,349
ftit annoying.

1006
00:41:16,349 --> 00:41:19,640
Għaliex aħna għandek tkun taf li Gabe
huwa tip ta 'speċjali f'dan il-programm.

1007
00:41:19,640 --> 00:41:21,440
Minħabba fil-fatt, huwa għandu pointer tiegħu stess.

1008
00:41:21,440 --> 00:41:24,860
Hu mhux biss qed mfakkar fil,
kif huwa kważi kulħadd hawn.

1009
00:41:24,860 --> 00:41:28,112
>> Allura meta l-kap tal-lista hija
jitneħħew, li f'idejha bżonn għall-bidla issa?

1010
00:41:28,112 --> 00:41:29,070
X'hemm isem tiegħek mill-ġdid?

1011
00:41:29,070 --> 00:41:29,450
>> UDJENZA: Christine.

1012
00:41:29,450 --> 00:41:31,408
>> DAVID J. Malan: Ninsab orribbli
fil ismijiet, apparentament.

1013
00:41:31,408 --> 00:41:34,011
Allura Christine u Gabe,
li f'idejha bżonn għall-bidla

1014
00:41:34,011 --> 00:41:36,510
meta aħna tipprova tneħħi Christine,
numru 5, mill-istampa?

1015
00:41:36,510 --> 00:41:37,550

1016
00:41:37,550 --> 00:41:38,820
OK, so ejja do Gabe.

1017
00:41:38,820 --> 00:41:40,950
Gabe għaddej għall-punt,
preżumibbilment, f'numru 9.

1018
00:41:40,950 --> 00:41:42,230

1019
00:41:42,230 --> 00:41:44,642
Imma dak li jmiss għandu jiġri?

1020
00:41:44,642 --> 00:41:46,600
UDJENZA: Christine għandhom
jkun null [inaudible].

1021
00:41:46,600 --> 00:41:50,244
DAVID J. Malan: OK, għandna probabbilment
make-- Smajt "null" x'imkien.

1022
00:41:50,244 --> 00:41:51,410
UDJENZA: Null u liberu tagħha.

1023
00:41:51,410 --> 00:41:51,855
DAVID J. Malan: NULL liema?

1024
00:41:51,855 --> 00:41:53,074
UDJENZA: Null u liberu tagħha.

1025
00:41:53,074 --> 00:41:54,490
DAVID J. Malan: Null u liberu tagħha.

1026
00:41:54,490 --> 00:41:55,422
Allura dan huwa faċli ħafna.

1027
00:41:55,422 --> 00:41:58,380
U huwa perfett li int issa sort
tal permanenti hemmhekk, ma jappartienux.

1028
00:41:58,380 --> 00:42:00,430
Għaliex inti kont qed
diżakkoppjat mill-lista.

1029
00:42:00,430 --> 00:42:02,820
You ħadthom effettivament ġiet
orfni mil-lista.

1030
00:42:02,820 --> 00:42:07,770
U hekk kellna aħjar sejħa b'xejn issa fuq
Christine li jagħti l-memorja lura.

1031
00:42:07,770 --> 00:42:10,240
Inkella kull darba we
tħassar node mil-lista

1032
00:42:10,240 --> 00:42:14,230
aħna jista 'jkun qed jagħmel il-lista
iqsar, iżda mhux attwalment qed jonqos

1033
00:42:14,230 --> 00:42:15,096
id-daqs fil-memorja.

1034
00:42:15,096 --> 00:42:17,720
U hekk jekk inżommu żżid u
żżid, żżid affarijiet mal-lista,

1035
00:42:17,720 --> 00:42:19,280
kompjuter tiegħi tista 'tikseb aktar bil-mod
u bil-mod u bil-mod,

1036
00:42:19,280 --> 00:42:21,740
għaliex jien baqgħalna ta '
memorja, anki jekk jien ma attwalment

1037
00:42:21,740 --> 00:42:25,580
użu bytes Christine ta
tal-memorja aktar.

1038
00:42:25,580 --> 00:42:28,500
>> Għalhekk fl-aħħar hemm oħrajn
xenarji, ta 'tneħħija course--

1039
00:42:28,500 --> 00:42:30,640
fin-nofs, it-tneħħija
fl-aħħar, kif rajna.

1040
00:42:30,640 --> 00:42:32,348
Iżda l-aktar interessanti
isfida issa hija

1041
00:42:32,348 --> 00:42:34,770
ser tkun li jikkunsidraw eżattament
dak il-ħin tal-ġiri hu.

1042
00:42:34,770 --> 00:42:36,640
Allura mhux biss inti tista 'żżomm tiegħek
biċċiet tal-karti, jekk, Gabe,

1043
00:42:36,640 --> 00:42:38,640
inti ma mind tagħti
kulħadd ballun stress.

1044
00:42:38,640 --> 00:42:42,100
Grazzi tant għall-lista marbuta tagħna
ta 'voluntiera hawn, jekk inti tista'.

1045
00:42:42,100 --> 00:42:45,320
>> [Applause]

1046
00:42:45,320 --> 00:42:46,700
>> DAVID J. Malan: Kull dritt.

1047
00:42:46,700 --> 00:42:51,110
Allura koppja ta analitika
mistoqsijiet Imbagħad, jekk I jistgħu.

1048
00:42:51,110 --> 00:42:59,670
Rajna dan notazzjoni qabel,
O kbar u omega, limiti ta 'fuq

1049
00:42:59,670 --> 00:43:02,520
u limiti aktar baxxi fuq il-
żmien ta 'xi algoritmu running.

1050
00:43:02,520 --> 00:43:04,950
Mela ejja jikkunsidraw biss
koppja ta 'mistoqsijiet.

1051
00:43:04,950 --> 00:43:07,090
>> Wieħed, u aħna qal li
qabel, x'inhu l-running

1052
00:43:07,090 --> 00:43:10,647
ħin tat-tfittxija għal
lista f'termini ta 'O big?

1053
00:43:10,647 --> 00:43:13,480
X'hemm marbuta massimu fuq it-tmexxija
żmien ta tiftix lista marbuta

1054
00:43:13,480 --> 00:43:16,340
kif implimentati mill-voluntiera tagħna hawn?

1055
00:43:16,340 --> 00:43:17,820
Huwa O kbir ta 'n, lineari.

1056
00:43:17,820 --> 00:43:20,630
Minħabba li fl-agħar każ,
l-element, bħal 55,

1057
00:43:20,630 --> 00:43:23,830
aħna tista 'tfittex għal jista' jkun fejn
Jack kien, it-triq kollha fl-aħħar.

1058
00:43:23,830 --> 00:43:28,250
U sfortunatament, b'differenza firxa
aħna ma tistax tikseb fancy dan iż-żmien.

1059
00:43:28,250 --> 00:43:31,820
Anke jekk kollha ta 'bnedmin tagħna kienu
magħżula minn elementi żgħar, 5,

1060
00:43:31,820 --> 00:43:35,900
it-triq kollha sa l-element akbar,
55, li normalment ħaġa tajba.

1061
00:43:35,900 --> 00:43:38,815
Imma dak ma dik is-suppożizzjoni
m'għadhomx inessu tagħmel?

1062
00:43:38,815 --> 00:43:39,775

1063
00:43:39,775 --> 00:43:40,650
UDJENZA: [inaudible]

1064
00:43:40,650 --> 00:43:40,920
DAVID J. Malan: Say mill-ġdid?

1065
00:43:40,920 --> 00:43:41,800
UDJENZA: aċċess Random.

1066
00:43:41,800 --> 00:43:43,049
DAVID J. Malan: aċċess Random.

1067
00:43:43,049 --> 00:43:46,330
U mbagħad dan ifisser nistgħu ebda
jibqgħux jużaw żerijiet dgħajfa, intwizzjoni,

1068
00:43:46,330 --> 00:43:49,365
u obviousness ta 'użu binarja
tfittxija u jaqsmu u conquer.

1069
00:43:49,365 --> 00:43:51,240
Minħabba li anke jekk aħna
bnedmin jistgħu ovvjament

1070
00:43:51,240 --> 00:43:54,610
tara li Andy jew Christian kienu
bejn wieħed u ieħor fin-nofs tal-lista,

1071
00:43:54,610 --> 00:43:57,670
aħna biss nafu li bħala
kompjuter permezz ta 'xkumar tal-lista

1072
00:43:57,670 --> 00:43:59,029
mill-bidu nett.

1073
00:43:59,029 --> 00:44:00,570
Allura aħna ħadthom rrinunzjaw li l-aċċess bl-addoċċ.

1074
00:44:00,570 --> 00:44:04,380
>> O Allura kbira ta 'n issa Hija l-ikona
marbuta fil-ħin tfittxija tagħna.

1075
00:44:04,380 --> 00:44:07,920
What about omega tat-tfittxija tagħna?

1076
00:44:07,920 --> 00:44:11,535
X'hemm-aktar baxx illegat dwar it-tiftix
għal xi numru f'din il-lista?

1077
00:44:11,535 --> 00:44:12,410
UDJENZA: [inaudible]

1078
00:44:12,410 --> 00:44:13,040
DAVID J. Malan: Say mill-ġdid?

1079
00:44:13,040 --> 00:44:13,420
UDJENZA: One.

1080
00:44:13,420 --> 00:44:13,800
DAVID J. Malan: One.

1081
00:44:13,800 --> 00:44:14,760
Allura waqt li kostanti.

1082
00:44:14,760 --> 00:44:17,020
Fl-aħjar każ, Christine hija
tabilħaqq fil-bidu tal-lista.

1083
00:44:17,020 --> 00:44:19,020
U aħna qed tfittex
numru 5, hekk sibna tagħha.

1084
00:44:19,020 --> 00:44:19,787
Allura l-ebda big deal.

1085
00:44:19,787 --> 00:44:22,370
Iżda hi ltqajna biex tkun fil-
bidu tal-lista f'dan il-każ.

1086
00:44:22,370 --> 00:44:23,745
What about xi ħaġa bħal Ħassar?

1087
00:44:23,745 --> 00:44:24,717

1088
00:44:24,717 --> 00:44:26,300
X'jiġri jekk inti tixtieq li tħassar element?

1089
00:44:26,300 --> 00:44:29,200
X'hemm-illegat fuq u inferjuri
fuq tħassir xi ħaġa minn marbuta

1090
00:44:29,200 --> 00:44:29,699
lista?

1091
00:44:29,699 --> 00:44:35,195

1092
00:44:35,195 --> 00:44:36,070
UDJENZA: [inaudible]

1093
00:44:36,070 --> 00:44:36,420
DAVID J. Malan: Say mill-ġdid?

1094
00:44:36,420 --> 00:44:37,067
UDJENZA: n.

1095
00:44:37,067 --> 00:44:38,900
DAVID J. Malan: n huwa
tabilħaqq l-ogħla marbuta.

1096
00:44:38,900 --> 00:44:41,700
Minħabba li fl-agħar każ nippruvaw
li tħassar Jack, bħal aħna biss għamlet.

1097
00:44:41,700 --> 00:44:43,050
Huwa tal-triq kollha fl-aħħar.

1098
00:44:43,050 --> 00:44:45,419
Iqarribna għal dejjem, jew
n passi biex issib lilu.

1099
00:44:45,419 --> 00:44:46,460
Allura dak rbit għoli.

1100
00:44:46,460 --> 00:44:47,430
C'est lineari, żgur.

1101
00:44:47,430 --> 00:44:50,970
U l-aħjar każ running time, jew
il-limiti aktar baxxi fil-każ aħjar

1102
00:44:50,970 --> 00:44:51,975
Ikun ħin kostanti.

1103
00:44:51,975 --> 00:44:54,600
Minħabba forsi nippruvaw li tħassar
Christine, u aħna biss jiksbu xxurtjati

1104
00:44:54,600 --> 00:44:55,558
hi tal fil-bidu.

1105
00:44:55,558 --> 00:44:56,350
Issa stenna minuta.

1106
00:44:56,350 --> 00:44:59,370
Gabe kien ukoll fil-bidu,
u aħna wkoll kellhom taġġorna Gabe.

1107
00:44:59,370 --> 00:45:01,150
Allura li ma kienx biss pass wieħed.

1108
00:45:01,150 --> 00:45:04,210
Allura huwa tabilħaqq kostanti
time, fl-aħjar każ,

1109
00:45:04,210 --> 00:45:06,345
biex tneħħi l-element iżgħar?

1110
00:45:06,345 --> 00:45:07,360

1111
00:45:07,360 --> 00:45:10,960
Huwa, anki jekk jista 'jkun tnejn,
tliet, jew saħansitra 100 linji ta 'kodiċi,

1112
00:45:10,960 --> 00:45:14,000
jekk huwa l-istess numru ta '
linji, mhux f'xi loop,

1113
00:45:14,000 --> 00:45:16,577
u indipendenti mid-daqs
tal-lista, assolutament.

1114
00:45:16,577 --> 00:45:18,660
Tħassar l-element fil-
il-bidu tal-lista,

1115
00:45:18,660 --> 00:45:21,940
anke jekk aħna jkollhom jittrattaw
Gabe, għadu żmien kostanti.

1116
00:45:21,940 --> 00:45:24,220
>> Allura din tidher qisha
pass enormi lura.

1117
00:45:24,220 --> 00:45:27,000
U dak ħela ta 'ħin
jekk, fil-ġimgħa u ġimgħa

1118
00:45:27,000 --> 00:45:30,250
żero kellna mhux biss
kodiċi pseudocode imma kodiċi attwali

1119
00:45:30,250 --> 00:45:35,780
biex jimplimentaw xi ħaġa li log
bażi n, jew log, pjuttost, ta 'n, bażi 2,

1120
00:45:35,780 --> 00:45:37,150
f'termini ta 'ħin għat-tmexxija tagħha.

1121
00:45:37,150 --> 00:45:40,710
Allura għaliex l-Heck kieku rridu nibdew
użu xi ħaġa bħal lista marbuta?

1122
00:45:40,710 --> 00:45:41,517
Yeah.

1123
00:45:41,517 --> 00:45:44,022
>> UDJENZA: Allura inti tista 'żżid
Elementi għall-firxa.

1124
00:45:44,022 --> 00:45:46,230
DAVID J. Malan: Allura inti tista '
jiżdiedu elementi għall-firxa.

1125
00:45:46,230 --> 00:45:47,550
U dan ukoll huwa tematika.

1126
00:45:47,550 --> 00:45:49,740
U aħna ser tkompli tara
dan, dan il-kummerċ off, ħafna

1127
00:45:49,740 --> 00:45:51,573
simili aħna stajt tidher
trade-off mal sort jingħaqdu.

1128
00:45:51,573 --> 00:45:54,606
Aħna jista 'verament tħaffef
tfittxija jew issortjar, pjuttost,

1129
00:45:54,606 --> 00:45:57,480
jekk nonfqu spazju daqsxejn aktar u
jkollhom chunk addizzjonali ta 'memorja

1130
00:45:57,480 --> 00:45:58,760
jew firxa għall tip jingħaqdu.

1131
00:45:58,760 --> 00:46:01,270
Iżda aħna jonfqu aktar
ispazju, imma aħna jiffranka ħin.

1132
00:46:01,270 --> 00:46:04,820
F'dan il-każ, aħna qed
tagħti up ħin, iżda aħna qed

1133
00:46:04,820 --> 00:46:08,170
jiksbu flessibilità,
dinamiżmu jekk inti se,

1134
00:46:08,170 --> 00:46:10,280
li huwa probabbilment karatteristika pożittiva.

1135
00:46:10,280 --> 00:46:11,520
>> Aħna wkoll qed infiq ispazju.

1136
00:46:11,520 --> 00:46:13,710
F'liema sens huwa marbut
lista aktar għaljin

1137
00:46:13,710 --> 00:46:15,700
f'termini ta 'spazju minn firxa?

1138
00:46:15,700 --> 00:46:18,379

1139
00:46:18,379 --> 00:46:19,920
Fejn l-ispazju żejda li ġejjin minn?

1140
00:46:19,920 --> 00:46:20,460
Yeah?

1141
00:46:20,460 --> 00:46:21,800
>> UDJENZA: [inaudible] pointer.

1142
00:46:21,800 --> 00:46:23,310
>> DAVID J. Malan: Yeah, aħna
ukoll għandek l-pointer.

1143
00:46:23,310 --> 00:46:25,560
Allura dan huwa minorly annoying
f'dak m'għadhomx am

1144
00:46:25,560 --> 00:46:27,780
I ħażna biss int
li jirrappreżentaw int.

1145
00:46:27,780 --> 00:46:30,990
Jien ħażna ta int u
pointer, li huwa wkoll 32 bits.

1146
00:46:30,990 --> 00:46:33,470
So jien litteralment irduppjar
l-ammont ta 'spazju involut.

1147
00:46:33,470 --> 00:46:36,040
Allura dak kompromess, iżda
li fil-każ ta 'int.

1148
00:46:36,040 --> 00:46:39,580
Ejja ngħidu li int mhux ħażna int,
iżda jissoponi kull wieħed minn dawn rettangoli

1149
00:46:39,580 --> 00:46:43,290
jew kull wieħed minn dawn il-bnedmin kien jirrappreżenta
kelma, kelma Ingliża li

1150
00:46:43,290 --> 00:46:46,430
jista jkun ta 'ħames karattri, 10
karattri, forsi anke aktar.

1151
00:46:46,430 --> 00:46:49,940
Imbagħad żżid biss 32 bits aktar
jista 'jkun inqas ta' big deal.

1152
00:46:49,940 --> 00:46:52,160
>> X'jiġri jekk kull wieħed mill-istudenti
fil-dimostrazzjoni

1153
00:46:52,160 --> 00:46:55,107
kienu litteralment structs studenti li
għandhom ismijiet u djar u forsi

1154
00:46:55,107 --> 00:46:57,065
numri tat-telefon u Twitter
mankijiet u simili.

1155
00:46:57,065 --> 00:46:59,564
Allura kollha ta 'l-oqsma bdejna
jitkellem dwar il-ġurnata l-oħra,

1156
00:46:59,564 --> 00:47:02,410
ħafna inqas ta 'big deal bħala
lymph tagħna jiksbu aktar interessanti

1157
00:47:02,410 --> 00:47:05,972
u kbar biex jonfqu, eh, addizzjonali
pointer biss biex jorbtuhom flimkien.

1158
00:47:05,972 --> 00:47:07,180
Iżda tabilħaqq, huwa kompromess.

1159
00:47:07,180 --> 00:47:09,560
U fil-fatt, il-kodiċi hija
aktar kumplessi, kif inti ser

1160
00:47:09,560 --> 00:47:11,770
tara permezz ta 'xkumar permezz
li eżempju partikolari.

1161
00:47:11,770 --> 00:47:14,302
Imma x'jiġri jekk kien hemm
xi Grail qaddis hawn.

1162
00:47:14,302 --> 00:47:17,010
X'jiġri jekk aħna ma jieħdu pass
lura iżda massiv pass 'il quddiem

1163
00:47:17,010 --> 00:47:19,180
u timplimenta data
istruttura via li aħna

1164
00:47:19,180 --> 00:47:22,870
jistgħu jsibu elementi bħall Jack jew
Christine jew xi elementi oħra

1165
00:47:22,870 --> 00:47:25,870
f'dan array fil-ħin kostanti vera?

1166
00:47:25,870 --> 00:47:26,920
Fittex huwa kostanti.

1167
00:47:26,920 --> 00:47:28,320
Ħassar hija kostanti.

1168
00:47:28,320 --> 00:47:29,570
Daħħal hija kostanti.

1169
00:47:29,570 --> 00:47:32,260
Kollha ta 'dawn l-operazzjonijiet huma kostanti.

1170
00:47:32,260 --> 00:47:33,750
Dan ikun Grail qaddis tagħna.

1171
00:47:33,750 --> 00:47:36,690
U li huwa fejn aħna
se jittellgħu ħin li jmiss.

1172
00:47:36,690 --> 00:47:38,600
Ara inti mbagħad.

1173
00:47:38,600 --> 00:47:39,371