[数论] HOJ 1015 Nearly prime numbers 筛素数

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jjaw2013

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分类专栏：数论 2014寒假文章标签：数论筛素数

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传送门：Nearly prime numbers

Nearly prime numbers

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	Source : Unknown
	Time limit : 1 sec		Memory limit : 1 M

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

1
6

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;
}