POJ 2262 Goldbach's Conjecture 数论

 题意：哥德巴赫猜想：任何两个大于4的偶数都等于两个奇素数之和。输入n， 求 n = a + b, a, b 为奇素数， 若不存在这样的a, b，输出Goldbach's conjecture is wrong。
#include <memory>
#include <iostream>
using namespace std;

int prime[1000000];

int main()
{
int i, j, n;
memset(prime,-1,sizeof(prime));
prime[0] = prime[1] = 0;
for ( i = 2; i <= 1000; i++ )
{
if ( prime[i] )
for ( j = 2; j*i <= 1000000; j++ )
prime[j*i] = 0;
}

while ( cin >> n && n )
{
for ( i = 2; i <= n/2; i++ )
if ( prime[i] && prime[n-i] )
{cout << n << " = " << i << " + " << n-i << endl; break;}
}
return 0;
}