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>> [Music kucheza]

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>> ZAMYLA CHAN: Jambo la kwanza nguvu
ilani kuhusu kupata ni kwamba tayari

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kuwa kanuni zilizoandikwa kwa ajili yetu.

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Hii inaitwa usambazaji code.

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Hivyo sisi siyo tu kuandika yetu wenyewe
kanuni kutoka mwanzo tena.

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Badala yake, sisi ni kujaza katika voids
katika baadhi ya kanuni kabla ya zilizopo.

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>> mpango find.c papo kwa idadi
kujaza haystack, utafutaji

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haystack kwa mtumiaji in sindano,
na haina kwa kuita aina na

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search, kazi inavyoelezwa
katika helpers.c.

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Hivyo find.c imeandikwa tayari.

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Kazi yako ni kuandika kuwanusuru.

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>> Basi ni nini sisi kufanya?

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Sisi ni utekelezaji wa kazi mbili.

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Search, ambayo anarudi kweli kama thamani
hupatikana katika haystack, kurudi

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uongo kama thamani ni
si katika haystack.

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Na kisha sisi ni pia kutekeleza aina
ambayo aina safu kuitwa maadili.

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>> Basi hebu kukabiliana na search.

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Search kwa sasa ni kutekelezwa kama
search linear, lakini unaweza kufanya mengi

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bora kuliko hiyo.

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Search linear unatekelezwa katika O
ya n wakati, ambayo ni polepole kabisa.

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Pamoja na kwamba, unaweza kutafuta
orodha wowote yake.

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Kazi yako ni kutekeleza search binary,
ambayo ina kukimbia wakati O logi n.

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Hiyo ni pretty haraka.

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>> Lakini kuna ahadi.

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Search kisha unaweza tu kutafuta
kwa njia ya orodha kabla ya yamepangwa.

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Kwa nini ni kwamba?

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>> Naam hebu tuangalie mfano.

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Kutokana na safu ya maadili, haystack,
tunakwenda kuwa na kuangalia

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kwa sindano.

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Na katika mfano huu,
integer tatu.

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njia ambayo search binary kazi ni kuwa
sisi kulinganisha thamani katikati ya

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safu ya sindano, kama ilivyo kwa jinsi
sisi kufunguliwa phonebook katikati

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ukurasa katika wiki sifuri.

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>> Hivyo, baada ya kulinganisha thamani ya katikati ya
sindano, unaweza kuondokana na ama

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upande wa kushoto au nusu wa kulia wa safu
na inaimarisha mipaka yako.

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Katika kesi hiyo, tangu tatu, sindano yetu,
ni chini ya 10, thamani ya kati,

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haki amefungwa unaweza kupungua.

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Lakini kujaribu kufanya mipaka yako
kama tight kama iwezekanavyo.

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Kama thamani katikati ni si sindano,
kisha unajua kwamba hawana haja ya

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ni pamoja na katika utafutaji wako.

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Basi, wewe ni haki amefungwa unaweza kaza
mipaka search tu kidogo kidogo zaidi,

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na kadhalika na kadhalika mpaka
kupata sindano yako.

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>> Basi ni nini pseudocode kuangalia kama?

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Vizuri wakati bado tuko kutafuta njia ya
orodha na bado na mambo ya

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kuangalia katika, sisi kuchukua katikati ya orodha,
na kulinganisha kwamba thamani katikati ya

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sindano yetu.

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Kama uko sawa, basi hiyo ina maana tumekuwa
kupatikana sindano na tunaweza

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kurudi kweli.

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>> Vinginevyo, kama sindano ni chini ya
thamani katikati, basi hiyo ina maana sisi

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unaweza kuondokana na nusu ya haki, na tu
kutafuta upande wa kushoto wa safu.

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Vinginevyo, tutaweza kutafuta
upande wa safu ya haki.

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Na mwisho, kama wewe huna lolote
mambo zaidi wa kushoto na kutafuta lakini

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sikuona sindano yako bado, basi
kurudi uongo kwa sababu sindano

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dhahiri si katika haystack.

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>> Sasa jambo nadhifu kuhusu pseudocode hii
katika kutafuta binary ni kwamba inaweza kuwa

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kufasiriwa kama ama iterative
au utekelezaji kujirudia.

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Hivyo itakuwa kujirudia kama wewe kuitwa
kutafuta kazi ndani ya search

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kazi ama nusu ya safu.

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Tutaweza cover kujirudia kidogo baadaye katika
Bila shaka, lakini tunajua kwamba ni

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chaguo kama Ningependa kujaribu.

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>> Sasa hebu tuangalie aina.

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Aina inachukua safu na integer
n, ambayo ni ya kawaida ya safu.

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Sasa kuna aina mbalimbali tofauti
wa kila aina, na unaweza kuangalia baadhi

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kaptula kwa demos na maelezo.

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kurudi aina kwa ajili yetu
aina ya kazi ni batili.

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Hivyo hiyo ina maana kwamba sisi siyo kwenda
kurudi safu yoyote kutoka aina.

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Sisi ni kweli kwenda na mabadiliko sana
safu kwamba ilipitishwa ndani yetu.

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>> Na kwamba inawezekana kwa sababu arrays ni
kupita kwa kumbukumbu katika C. Sasa tutaweza

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kuona zaidi kuhusu hili baadaye, lakini
tofauti muhimu kati ya kupita

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katika kitu kama integer na kupita
katika safu, ni kwamba wakati

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kupita katika integer, C ni kwenda tu
kufanya nakala ya kwamba integer na kupita

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kwa kazi.

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awali variable haitabadilika
mara moja kazi ni kumaliza.

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Na safu, kwa upande mwingine, ni
si kwenda kufanya nakala, na wewe utakuwa

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kweli kuwa editing
sana safu yenyewe.

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>> Hivyo aina moja ya aina ni
uteuzi aina.

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aina uteuzi kazi kwa kuanzia saa
mwanzo, na kisha iterate

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juu ya kupata na hiki ndogo.

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Na kisha kubadilishana kwamba ndogo
hiki kwa moja kwanza.

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Na kisha hoja ya hiki pili
, Kupata ijayo ndogo

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hiki, na kisha kubadilishana kwamba pamoja na
hiki pili katika safu kwa sababu

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hiki kwanza tayari yamepangwa.

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Na hivyo basi kuendelea kwa kila
hiki katika kutambua ndogo

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thamani na swapping nje.

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>> Kwa maana Mimi ni sawa na 0, hiki kwanza sana
kwa n minus 1, wewe ni kwenda kulinganisha

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kila thamani ya pili baada ya kuwa na kupata
index ya thamani ya chini.

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Mara baada ya kupata thamani ya chini index,
unaweza kubadilishana kwamba thamani ya safu

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kiwango cha chini na safu I.

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>> Aina nyingine ya aina hiyo unaweza
kutekeleza ni Bubble aina.

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Hivyo Bubble aina iterates juu ya orodha
kulinganisha mambo karibu na

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swapping mambo ambayo
ni ili sahihi.

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Na kwa njia hii, hiki kubwa
mapenzi Bubble hadi mwisho.

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Na orodha ni vyema mara moja hakuna zaidi
mambo wamekuwa walibadilishana.

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>> Hivyo wale ni mifano miwili ya aina
algorithms kwamba unaweza kutekeleza kwa

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kupata mpango.

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Mara baada ya kumaliza aina, na wameweza
kufanyika search, wewe ni kumaliza.

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Jina langu ni Zamyla, na hii ni CS50.

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>> [Music kucheza]