Primes

1
2
3
4
5
17
0

1: no
2: no
3: yes
4: no
5: yes
6: yes

AC代码：

#include <map>
#include <set>
#include <cmath>
#include <deque>
#include <queue>
#include <stack>
#include <cstdio>
#include <cctype>
#include <string>
#include <vector>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
#define LL long long
#define INF 0x7fffffff
using namespace std;

const int maxn = 20000;
int prime[20000];

void init() {
	prime[1] = 2;
	for(int i = 2; i < maxn; i ++) 
		if(prime[i] == 0) {
			prime[i] = 1;
			for(int j = i * 2; j < maxn; j += i) {
				prime[j] = 2;
			}
		}
	prime[2] = 2;
}

int main() {
	init();
	int cas = 1;
	int a;
	while(scanf("%d", &a) != EOF) {
		if(a == 0) break;
		
		if(prime[a] == 1) {
			printf("%d: yes\n", cas ++);
		}
		else if(prime[a] == 2) {
			printf("%d: no\n", cas ++);
		}
	}
	return 0;
}