HduOJ 2162 - Primes

 1 #include<iostream>
 2 #include<cmath>
 3 #include<cstdio>
 4 using namespace std;
 5 #define N 16001
 6 bool prime[N];
 7 void init(){
 8     for(int i = 0; i <= N ; i++){
 9         prime[i] = true;
10     }
11     
12     
13     for(int i = 3; i < N; i++){
14         int tot = (i + 1) / 2;
15         for(int j = 2; j <= tot; j++){
16             if(i % j == 0){
17                 prime[i] = false;
18                 break;
19             }
20         }
21     }
22     prime[1] = false;
23     prime[2] = false;
24      
25 }
26 int main(){
27     init();
28     int n;
29     int cas = 1;
30     while(scanf("%d",&n) , n>0){
31         printf("%d: ",cas++);
32         if(prime[n])
33             printf("yes\n");
34         else
35             printf("no\n");
36     }
37     return 0;
38 }