Dlya nachala posmotrite zakon slozheniya v internete.
Zadacha sleduyuschaya:
kod dlya zamka sostoit iz 7 alphanumeric characters:
LLNLNLN,gde L-letter(A-Z), N- chislo ot 0 do 9
1)Naiti kolichestvo vozmozhnyh pravilnyh kombinatsii pri uslovii,chto v kode dolzhna byt iskluchitelno(exhaustively) odna "A"?
Reshenie:
Znaya, chto my imeem delo s kombinatsiei LLNLNLN dostatochno vybrat bukvu A i poocheredno polozhit ee v pozitsii 0,1,3,5(index kak v python list-nachinaetsya s 0) i iskluchit iz ostalnykh letter-pozitsii:
Index 0: 1(polozhili v nulevuyu pozitsiu)*25(Vychli "A")*10*25*10*25*10
Index 1:25*1*10*25*10*25*10
index 3+Index 5: 2*25^3*10^3(result pribavili k predyduschemu cumaulative result, t.e. k index 1 i index 0)
2) Zadacha na extraction.
Igraem v bingo(analog loto). Shary pronumerovany ot 0 do 100.
Vopros:
a)Skolko extraction my mozhem osuschestvit?
b)S iskluchitelno odnim nechetnym?
c)S dvumya chetnymi?
Mozhno primenit formulu permutations without repitition ili logicheski:
Reshenie:
a) Dlya vybora pervogo shara u nas 100 variantov dlya vybora vtorogo-99, tretiego- 98 itd.
Final result: 100*99*98*97*96
po formule- 100!//(100-5)!
b)Total nechetnykh=total chetnykh=50
Analogichno a):
50*49*48*47(vybrali chetnye)*50(vybor edinstennogo nechetnogo)- order ne vazhen
c)50*49*50*49*48(Nadeus, poyasneniya ne nuzhny)
Do novyh vstrech!