[数论] HOJ 1015 Nearly prime numbers 筛素数

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Nearly prime numbers

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Submitted : 4684, Accepted : 830

Nearly prime number is an integer positive number for which it is possible to find such primes P₁ and P₂ that given number is equal to P₁*P₂. There is given a sequence on N integer positive numbers, you are to write a program that prints Yes if given number is nearly prime and No otherwise.

Input

Input consists of N+1 numbers. First is positive integer N (1<=N<=50000). Next N numbers followed by N. Each number is not greater than 10⁹. All numbers separated by whitespace(s).

Output

Write a line in output for each number of given sequence. Write Yes if given number is nearly prime and No in other case.

Sample Input

16

Sample Output

Yes

解题报告：

题意很简单。就是一个数是否能化成两个素数相乘。表示此题就是卡内存。代码如下：

#include <stdio.h>bool isPrime(int n){    for (int m = 2; m * m <= n; m++)        if(n % m == 0)            return 0;    return 1;}int main(){    int prime[3500] = {2};    int i = 1, j = 3;    while (i < 3500){        if(isPrime(j))            prime[i++]=j;        j+=2;    }    int t, n;    scanf("%d", &t);    while (t--){        scanf("%d", &n);        bool b = false;        for(i = 0; prime[i] * prime[i] <= n; i++)            if(n%prime[i]==0&&isPrime(n/prime[i])){                printf("Yes\n");                b = true;                break;            }        if(!b)            printf("No\n");    }    return 0;}