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>> ZAMYLA Chan: L-ewwel ħaġa inti tista '
avviż dwar jsibu hi li aħna diġà

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jkunu kodiċi miktub għalina.

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Din tissejjaħ kodiċi distribuzzjoni.

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Allura aħna mhux biss bil-miktub tagħna stess
kodiċi mill-bidu aktar.

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Pjuttost, aħna qed timla l-vojt
f'xi kodiċi pre-eżistenti.

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>> Il-programm find.c iqajjem għal numri
biex timla l-haystack, tfittxijiet-

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Haystack għal utent sottomessa labra,
u dan tagħmlu billi ċċempel it-tip u

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tiftix, il-funzjonijiet definiti
fil helpers.c.

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Allura find.c hija diġà bil-miktub.

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Xogħol tiegħek huwa li tikteb helpers.

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>> Allura dak li qed nagħmlu?

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Aħna qed timplimenta żewġ funzjonijiet.

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Search, li jirritorna minnu jekk valur
jinstab fil-haystack, jirritornaw

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falz jekk il-valur huwa
mhux fil-haystack.

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U allura aħna qed timplimenta wkoll sort,
li xorta l-array imsejħa valuri.

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Mela ejja tindirizza search.

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>> Search hija implimentata bħalissa
bħala search lineari.

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Iżda int tista 'tagħmel ħafna aħjar minn dik.

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Tfittxija lineari hija implimentata O ta 'n
time, li huwa pjuttost bil-mod, għalkemm

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tista 'tfittex kull lista mogħtija lilha.

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Xogħol tiegħek huwa li timplimenta tfittxija binarju,
li tkun run time O ta 'log n.

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Li pretty fast.

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>> Iżda hemm stipulazzjoni.

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Tfittxija Binarju tista 'tfittex biss
permezz ta 'listi magħżula minn qabel.

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Għaliex huwa li?

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Well, ejja nħarsu lejn eżempju.

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Minħabba l-firxa ta 'valuri, il-haystack,
aħna qed tmur biex tkun tfittex

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għal labra, u f'dan il-
eżempju, il-integer 3.

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>> Il-mod li tfittxija binarju jaħdem huwa li
inqabblu l-valur medju ta '

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il-firxa tal-labra, ferm simili kif
aħna fetħet ktieb tat-telefon għall-nofs

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paġna fil f'Ġimgħa 0.

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Allura wara tqabbil tal-valur medju biex
il-labra, inti tista 'jarmi jew il-

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xellug jew in-nofs lemini tal-array
billi issikkar limiti tiegħek.

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F'dan il-każ, mit-3, labra tagħna, huwa
anqas minn 10, il-valur tan-nofs, il-

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dritt marbut jistgħu jnaqqsu.

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>> Iżda jippruvaw jagħmlu limiti tiegħek
stretta daqs kemm possibbli.

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Jekk il-valur tan-nofs mhuwiex il-labra,
imbagħad inti taf li inti m'għandekx bżonn li

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tinkludih fit-tfittxija tiegħek.

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Allura dritt tiegħek marbuta tista issikka l-
limiti tat-tiftix biss ftit żgħira aktar,

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u hekk u ibqa 'sejjer hekk, sakemm
issib labra tiegħek.

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>> Allura dak li ma l-psewdo
kodiċi look like?

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Well, filwaqt li aħna qed għadhom tfittex permezz
il-lista u għad għandhom

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elementi biex tfittex fil, nieħdu l-nofs
tal-lista u jqabblu li

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valur medju għall-labra tagħna.

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Jekk dawn qed ugwali, allura dan ifisser konna
sabet il-labra, u nistgħu

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ritorn vera.

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>> Inkella, jekk il-labra tkun inqas minn
il-valur tan-nofs, allura dan ifisser li aħna

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jista 'jarmi l-nofs tal-lemin u biss
tfittxija ix-xellug tal-array.

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Inkella, aħna ser tfittex il-
lemin tal-array.

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U fl-aħħar, jekk inti ma għandekx xi
aktar elementi xellug ta 'tiftix imma int

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ma sabu labra tiegħek għadhom,
allura inti tirritorna falza.

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Minħabba li l-labra definittivament
mhuwiex fil-haystack.

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>> Issa, ħaġa waħda pulita dwar dan psewdo
kodiċi fit-tfittxija binarju huwa li tista '

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tiġi interpretata jew bħala iterattiv
jew l-implimentazzjoni rikursiv.

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Għalhekk ikun rikursivi jekk inti imsejħa
il-funzjoni ta 'tfittxija fil-search

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jiffunzjonaw fuq kull nofs il-firxa.

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Aħna ser ikopru recursion daqsxejn
aktar tard fil-kors.

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Imma nafu li hija possibilità
jekk inti tixtieq li jippruvaw.

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