Блог пользователя Imapaj

Автор Imapaj, история, 9 лет назад, По-английски

Hi Codeforces :P.

I'm trying to solve a problem about how many divisors has a Number.

In the Solutions Statements say that:

if we obtain only the factors of the number up to cube root of N.

then we obtain N = C*(factorization_of_N_up_to_cube_root)

and C can be only 1 or prime or prime*prime.

but i dont understand why.

Can see the entire explanation in the Presentation of the Solution, Problem F.

Presentation of Solutions|Problem F

I would greatly appreciate your help.

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9 лет назад, # |
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If C is prime*prime*prime (or more primes) then N >= C >= prime*prime*prime. It follows that one of those primes <= cubic root of N, a contradiction.

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9 лет назад, # |
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I have a quection: how to check for O(logN) whether C is prime? Is there any deterministic way? Or just Millen-Rabin?