HDU 1016 - Prime Ring Problem [简单DFS]

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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;}

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