HDU 1016 - Prime Ring Problem [简单DFS]

不想说这题有多么水了，最简单的DFS题了，但是！我花了N天在杭电用G++交了20多遍一直超时，最后改C++交过了！！

这是什么情况！！无语了！！

#define _CRT_SECURE_NO_WARNINGS
#include <cstdio>
#include <cstring>
#include <cstdlib>

const int maxn = 1024;
bool checked[maxn] = { 1, 1 };
int pri[maxn], tot = 0;
int n, res[22], kase = 0, vis[22];

void init(){
    for (int i = 2; i < maxn; ++i){
        if (!checked[i]) pri[tot++] = i;
        for (int j = 0; j < tot && pri[j] * i < maxn; ++j){
            checked[pri[j] * i] = 1;
            if (!(i % pri[j])) break;
        }
    }
}

void DFS(const int d){
    if (d == n){
        if (!checked[1 + res[d - 1]]){
            for (int i = 0; i < n; ++i)
                printf("%d%c", res[i], i == n - 1 ? '\n' : ' ');
        }
        return;
    }
    for (int i = 2; i <= n; ++i){
        if (!vis[i] && !checked[i + res[d - 1]]){
            vis[i] = 1;
            res[d] = i; DFS(d + 1);
            vis[i] = 0;
        }
    }
}

int main(){
    init();
    while (~scanf("%d", &n)) {
        printf("Case %d:\n", ++kase);
        memset(vis, 0, sizeof(vis));
        res[0] = 1; vis[1] = 1;
        DFS(1);
        printf("\n");
    }
    return 0;
}