yusijia’s blog hdu 2098

#include <cstring>

int mark[10100];

int ()
{
    memset(mark, 0, sizeof(mark));
    for(int k = 2; k <= 10000; k++)if(mark[k] == 0){
        for(int j = k + k; j <= 10000; j += k)
            mark[j] = 1;
    }
    int data, sum;
    while(scanf("%d", &data) != EOF && date){
        sum = 0;
        for(int i = date / 2; i >= 2; i--){
            if(mark[i] == 0 && mark[data - i] == 0 && i != data - i)
                sum++;
        }
        printf("%dn", sum);
    }
    return 0;
}