SGU 113 Nearly prime numbers

SGU_113

对数分解素因子即可，如果最后素因子的个数为1或者大于2自然无解。

#include<stdio.h>#include<string.h>#include<math.h>#define MAXD 100010#define D 100000int isprime[MAXD];int N;void prepare(){long long int i, j;    memset(isprime, -1, sizeof(isprime));for(i = 2; i < D; i ++)if(isprime[i])for(j = i * i; j < D; j += i)                isprime[j] = 0;}int check(int x){int i, k, ok, num = 0;while(x != 1 && num <= 2)    {        k = (int)sqrt(x + 1.0);for(i = 2; i <= k; i ++)if(isprime[i] && x % i == 0)            {                ++ num;                x /= i;break;            }if(i == k + 1)        {            ++ num;            x /= x;        }    }if(num == 2)return 1;elsereturn 0;}int main(){int i, x;    prepare();    scanf("%d", &N);for(i = 0; i < N; i ++)    {        scanf("%d", &x);if(x < 2 || !check(x))            printf("No\n");else            printf("Yes\n");    }return 0;}

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