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[Powered by Google Translate] Tommy MACWILLIAM: Hebu majadiliano kuhusu tanzi, moja ya kawaida

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programu constructs tutaweza kuona katika CS50.

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Tutaweza kutumia loops wakati tunataka kufanya

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kazi zaidi ya mara moja.

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Kwa mfano, sisi kutaka magazeti "hi" mara 100 au magazeti

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nje barua zote za alfabeti.

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Katika wote wa kesi hizi, tuna jambo moja tunataka kufanya

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mara nyingi, magazeti kitu nje.

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Hata hivyo, nini sisi magazeti nje kila wakati wanaweza kutofautiana.

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Hivyo tunaweza kufanya kitu tofauti kidogo juu ya kila

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iteration, au kukimbia kwa njia ya kitanzi.

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Tutaweza kuona aina tatu tofauti za matanzi katika C, wakati

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tanzi, kwa tanzi, na kufanya wakati matanzi.

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Ingawa haya matatu aina ya matanzi kuwa syntax tofauti,

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mawazo nyuma yao ni sawa.

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Tutaweza kufafanua baadhi block ya maadili ndani ya braces curly,

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linaitwa mwili wa kitanzi, kwamba tunataka wauawe

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baadhi idadi ya nyakati.

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Kwa kubadilisha maadili ya vigezo kutumika katika mwili, sisi

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wanaweza kufanya kitanzi wetu kufanya kitu tofauti kila wakati ni kukimbia.

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Kwa yoyote kitanzi sisi kuandika, tutaweza pia haja ya kuamua wakati

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kitanzi kuacha mbio.

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Kama hatuwezi kufanya hivyo, basi trusty wetu kompyuta itaendelea

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kuendesha kwamba kitanzi mpaka sisi kuua mpango.

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Katika Scratch, tunaweza kutumia kurudia n mara

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kuzuia kuunda kitanzi.

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Wote wa vipande ndani ya kuzuia kwamba alisema kurudia 10

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itakuwa kukimbia mara 10.

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Na kisha, tunatarajia kuendelea na vipande baada ya kitanzi kwamba.

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Hivyo kuacha yetu hali ilikuwa tu, block hii imekuwa

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kukimbia mara 10.

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Basi hebu recreate hii katika C. Ili Scratch kuhakikisha

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kwamba vipande ndani ya kuzuia kurudia ni kunyongwa

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hasa mara 10, Scratch inahitaji kuweka wimbo wa kila

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utekelezaji wa kuzuia kurudia.

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Ili kuweka wimbo wa jinsi mara nyingi kitanzi yetu mwili imekuwa

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kunyongwa, hebu kuunda variable kuitwa i.

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Tutaweza kuanza i mbali katika sifuri, tangu kitanzi wetu

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haijawahi kuendesha bado.

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OK

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Sasa tutaweza kutumia Keyword wakati kuanza mbali kitanzi yetu.

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Sasa tutaweza haja ya kufikiri wakati kitanzi wetu kuacha, lakini

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hebu kuondoka hii kwa sasa na kisha kuja nyuma yake.

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Wote haki.

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Ndani ya kitanzi wetu, wacha tu magazeti ujumbe nje, kama

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"Hi." Tunaweza kutumia kazi printf kwa hili.

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Wote haki.

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Hivyo sasa tutaweza kurekodi kwamba iteration ya mwili kitanzi ina

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alinyongwa.

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Tunaweza kufanya hivyo kwa kuongeza 1, au incrementing, counter wetu

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variable, i.

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Ili kufanya hivyo, tunaweza kusema i ni sawa na i plus 1, au zaidi

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tu, i plus plus.

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Mkuu.

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Hivyo sasa tunaweza kuona kwamba kila wakati kitanzi yetu ni kukimbia, yetu

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variable counter huenda juu kwa moja.

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Hivyo sisi kujua hasa jinsi wengi iterations tumekuwa kukimbia hadi sasa.

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Baada ya mmoja iteration ya kitanzi, thamani yetu

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ya i itakuwa 1.

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Baada iterations mbili, i itakuwa 2.

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Na baada ya iterations 10, i itakuwa 10.

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Hivyo, kama tunataka kukimbia hii kitanzi hasa mara 10, basi

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hii ni wakati tunataka kuacha.

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Hivyo tunataka kukimbia hii kitanzi wakati i ni chini ya 10, na

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hiyo ni sawa kabisa tutaweza kuandika, wakati i

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ni chini ya 10.

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Hali hii inaonekana tu kama hali ya sisi kutumika katika iwapo

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mwingine vitalu.

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Baada ya mwili wa kitanzi yetu imekuwa kunyongwa, mpango wetu

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utaongezeka nyuma hadi hali matanzi.

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Kama hali ni kweli, basi mwili wa

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kitanzi utaendeshwa tena.

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Kama hali ni tena kweli, basi kitanzi wetu hautakuwa

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kukimbia tena na hoja juu ya line ya pili ya code

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chini ya kitanzi yetu.

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Wote haki.

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Basi hebu tuangalie aina ya pili ya

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kitanzi, kwa kitanzi.

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Next Keyword wakati, katika mabano, tulikuwa na jambo moja,

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hali ambayo inahitajika kuwa ni kweli kwa

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mwili kitanzi kwa kuwa na kukimbia.

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Hiyo ina maana tulikuwa na kujenga variable yetu counter nje

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ya kitanzi na kumbuka increment ni wakati fulani

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ndani ya kitanzi.

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header kwa wetu kwa kitanzi, kwa upande mwingine, ina tatu

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sehemu, ambayo kila mmoja itakuwa waliojitenga semicolon.

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Katika tatu yetu ya kwanza, tunaweza kutangaza yoyote counter au msaidizi

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vigezo tunatarajia kutumia katika kitanzi yetu.

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Katika mazoezi, hii inaweza kuwa kweli kusaidia.

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Sisi kwa kweli hawana haja ya kuwa kutofautiana, i, baada ya wakati wetu

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kitanzi ina kukimbia, hivyo sisi kweli haipaswi kuyatangaza

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nje ya kitanzi.

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tatu ya pili itakuwa hali ya kuwa lazima kuwa kweli

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kwa ajili ya mwili kuuawa tena, kama tu

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katika wakati kitanzi yetu.

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Katika tatu ya mwisho mwisho, tunaweza kuendesha taarifa kwamba itakuwa

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kunyongwa baada ya kila iteration ya kitanzi, hivyo hatuna

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kujenga ndani ya mwili kitanzi.

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Basi hebu andika kwa kitanzi kwamba makosa chini 5-1.

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Tutaweza kuanza na keyword kwa.

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Tunaweza kujenga variable counter ya kwanza, ambayo tutaweza

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kuweka 5 wakati huu tangu tuko kuhesabu chini,

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ikifuatiwa na semicolon.

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Next ni hali yetu, ambayo tutaweza kurudi.

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Tatu, tunatarajia pungufu variable yetu counter baada ya

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kila iteration ya kitanzi.

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Hivyo badala ya kusema i plus plus, tutaweza kusema i bala bala.

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Wote haki.

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Hivyo tunataka mwili kitanzi kukimbia wakati i bado ni

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kubwa kuliko 0.

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Katika mwili wa kitanzi, hebu magazeti nje thamani ya i.

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Kwa kufanya hivyo, tutaweza kutumia kazi printf, kwa kutumia d%

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placeholder.

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Kumbuka, placeholder kwamba itakuwa kubadilishwa kwa

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thamani ya i.

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Hatimaye, hebu kuongeza taarifa baada yetu kwa kitanzi.

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Wakati sisi kukimbia hii kitanzi, i kuanza mbali katika 5,

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hivyo 5 itakuwa printed.

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Mara moja i anapata 0, hali muendelezo, i ni

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kubwa kuliko 0, tena kushikilia.

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Hivyo kitanzi wetu kuacha utekelezaji, na tutaweza kuona

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Taarifa baada ya kitanzi.

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Basi hebu kukimbia hii code.

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Kwanza, tutaweza kukusanya

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countdown.c na kufanya Countdown.

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Sasa, tunaweza kukimbia hii kificho na. Countdown /.

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Katika matanzi wakati wote na kwa tanzi, yetu muendelezo

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sharti kuwa checked kabla ya mwili

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ya kitanzi ni kunyongwa.

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Hiyo ina maana kuwa, kama hali yetu si ya awali

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kweli, basi mwili wa kitanzi wetu kamwe kuwa na kukimbia.

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Hivyo ni wakati mwingine muhimu ya kuangalia hali ya baada ya

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mwili wa kitanzi badala ya kabla yake.

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Basi hebu kuandika kitanzi kuchochea mtumiaji kwa idadi

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mpaka idadi chanya ni hutolewa.

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Kama mtumiaji pembejeo idadi hasi, tutaweza nataka kuwauliza

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kwa idadi mwingine.

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Hivyo tutaweza unataka hii haraka kuwa ndani ya

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mwili mbali kitanzi.

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Hata hivyo, wakati kitanzi ni kukimbia kwa mara ya kwanza, user

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hakutupa idadi bado.

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Hivyo haina mantiki kwa kuangalia kama ni chanya.

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Badala yake, tutaweza wanataka kuangalia idadi baada ya mwili wa

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kitanzi ni kukimbia.

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Tunaweza kufanya hili kwa do wakati kitanzi.

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Kwanza, tutaweza kujenga variable, n, kwamba itafanya

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mtumiaji pembejeo.

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Sasa tutaweza kutumia Keyword do, ikifuatiwa na braces curly kwamba

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itaanza mbali mwili wa kitanzi yetu.

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Katika mwili, tunaweza kuchochea mtumiaji kwa idadi na

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GetInt kazi.

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Sasa, sisi utasikia wanataka mwili wa kitanzi hii nitafanya tena kama

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user typed idadi hasi, hivyo tutaweza kusema wakati n

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ni chini ya 0.

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Notice semicolon hapa baada ya taarifa ya muda.

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Basi hebu kukimbia hii code.

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Kwanza, tutaweza kukusanya hii na kufanya mazuri.

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Sasa tunaweza kuendesha programu na / chanya..

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Kama sisi kutoa mpango huu idadi hasi, kama hasi

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4, basi tutaweza hutaulizwa tena kwa idadi tangu

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hali ya do wetu wakati kitanzi ilikuwa kweli.

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Mara sisi kutoa idadi chanya, kama 8, kisha

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hali ya do wetu wakati kitanzi tena kuwa kweli.

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Hivyo kitanzi si lazima ifanyike tena.

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Na hiyo ni kwa aina tatu za matanzi tutaweza kutumia katika C.

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Jina langu ni Tommy, na hii ni CS50.