poj 2262 Goldbach's Conjecture

素数判定...很简单= =.....只是因为训练题有，所以顺便更~

 #include<cstdio>
 #include<memory.h>
 #define maxn 5000005
 int prime[maxn];
 void f()
 {
     memset(prime,,sizeof(prime));
     prime[] = prime[] = ;
     for(int i = ; i < maxn; i++)
     {
         if(!prime[i])
         {
             for(int j =  * i; j < maxn; j += i)
                 prime[j] = ;
         }
     }
 }
 int main()
 {
     freopen("input.txt","r",stdin);
     int n,i;
     f();
     while(scanf("%d",&n) && n)
     {
         for(i = ; i < n /; i += )
         {
             if(!prime[i] && !prime[n - i])
                 break;
         }
         printf("%d = %d + %d\n",n,i,n-i);
     }
     return ;
 }