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>> Rob BOWDEN: Hi, mimi nina Rob.

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Na wakati katika Rome, basi mpango wa
kama Waroma wanavyofanya.

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Kwa hiyo, jambo la kwanza tunahitaji kufanya ni kuangalia
kuhakikisha kweli user aliingia

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idadi hiyo tunataka mzunguko wa kila
tabia kwa katika mstari amri.

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>> Hivyo, sisi kuangalia.

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Ni argc sawa na 2?

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Kama siyo, hiyo ina maana user ama
hakuingia idadi katika

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mstari amri au waliingia wengi mno
mambo katika mstari amri, ambayo

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kesi hatujui nini cha kufanya
na wengine wa mambo.

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Hivyo, kwa muda mrefu kama argc mara mbili, tunaweza
kuendelea na wengine wa mpango.

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>> Sasa, kumbuka kwamba argv
1 ni daima kamba.

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Lakini tunataka kutibu kama integer.

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Kwa hiyo, sisi kutumia atoi kazi hiyo ni
zilizotajwa p kuweka spec kubadili

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kamba argv 1 kwa integer,
na sisi kuhifadhi kwamba katika muhimu.

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Tunataka kuhakikisha kuwa integer
kwamba alikuwa aliingia ni si mbaya.

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Na kama ilikuwa, tunataka magazeti kwamba kwa
user kwamba wao ni hawaruhusiwi

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kufanya hivyo, na kurudi.

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>> Kwa hiyo, sasa tuna halali
idadi kutoka kwa mtumiaji.

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Lakini tunahitaji kupata kamba kutoka
user kwamba tunataka fumbo.

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Hivyo sisi kutumika kufanya-wakati kitanzi na kutumia kupata
kamba kupata kamba hii kutoka

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user, na kuendelea kupata string
mpaka kwa kweli

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kuingia kamba halali.

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>> Mara baada ya sisi na kamba kwamba, sisi
unaweza kwenda kwenye encrypt yake.

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Kwa hiyo, hili kwa kitanzi ni kufanya
kwamba encryption.

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Taarifa kwamba sisi ni iterating kutoka i
sawa na 0 t njia yote hadi i usawa

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n, ambapo n inaelezwa kama urefu wa
ujumbe wetu, ambapo ujumbe ni

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kamba kwamba mtumiaji aliingia.

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>> Hivyo sisi ni iterating juu ya yote
wahusika katika kamba.

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Na kama tabia ni uppercase, basi
tunakwenda kuhama ni kutumia hii

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formula, ambayo tutaweza
kupata katika pili.

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Na kama ilikuwa Herufi za chini, kisha
tutaweza kuhama ni kutumia hii ni

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sawa sana formula.

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Na kama ilikuwa wala uppercase wala
lowercase barua - kwa mfano,

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inaweza kuwa idadi au alama - kisha sisi
si kwenda kufanya kitu chochote yake.

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>> Hivyo, nini ni kanuni hizi?

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Naam, ni jinsi gani sisi kuhama tabia ya A?

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Tunataka kutibu tabia ya
kama idadi 0.

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Na tunataka kutibu tabia ya
B kama namba 1, na kadhalika.

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Ni wahusika 0 na kwanza
wa alfabeti na kadhalika.

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>> Hivyo hapa, ujumbe i minus A zinatakiwa
kutupatia mahali numeric ya

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barua katika alfabeti.

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Hivyo kama ujumbe i ni, hii
ni kwenda kutupa 0.

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Sasa, tunataka kuongeza kuwa the
idadi hiyo user anataka

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mzunguko wa barua ya.

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Hivyo, kama waliingia 3, kisha kama ujumbe
i mara, hii itatupa 0 na pamoja na

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muhimu kutupa 3.

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>> Basi sasa, sisi ni kuzingatia
nafasi ya tatu katika alfabeti.

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Tutaweza kuona kwa nini tunahitaji Mod
na num barua ya pili.

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Lakini hatimaye, tunataka kuongeza juu ya
mwisho tena kuhama sisi nyuma katika

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Maadili ASCII kwa wahusika hawa
badala ya maeneo namba katika

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alfabeti ya wahusika hawa.

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>> Hivyo, kwa nini sisi Mod kwa barua num?

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Kumbuka kwamba tunataka kufungia
kutoka mwisho wa alfabeti ya

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mwanzo wa alfabeti.

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Hivyo kama user iliingia Z, kisha
subtracting A na kwamba ni kwenda

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kutupatia 25.

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Na kama muhimu walikuwa 3, kisha
tunakwenda na 28.

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Lakini Z lazima wrap karibu na ABC, hivyo 28
mod num barua, ambayo ni hash inavyoelezwa

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kama 26 kutarajiwa, ni kwenda kutoa
sisi 2, ambapo C ni barua ya pili ya

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alfabeti, kama unakumbuka kwamba A ni
0 barua ya alfabeti.

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>> Hivyo ndiyo sababu tunahitaji
mod kwa barua num.

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Sasa, sisi haja ya kufanya kitu kimoja halisi
kwa barua lowercase, ila

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kumbuka kwamba wakati sisi ni kushughulika na
barua lowercase, wana tofauti

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Maadili ASCII.

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Na hivyo tunahitaji Ondoa na kuongeza juu ya
kuhama chini kutoka lowercase

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Maadili ASCII na kisha kurejea
awali lowercase maadili ASCII.

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>> Na hatimaye, kwamba utakuwa kutupa
ujumbe wetu uliosimbwa.

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Na mwisho, sisi tu magazeti nje
kwamba ujumbe, na hiyo ni yake.

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Jina langu ni Rob, na mara Caesar.

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