hdu 4016搜索

这题看完本来以为是找规律的，可找了半天也没找出啥规律，翻了一下解题报告，说是搜索加剪枝，学了一下，就过了。

/*

 * hdu4016/win.cpp

 * Created on: 2012-11-9

 * Author    : ben

 */

#include <cstdio>

#include <cstdlib>

#include <cstring>

#include <cmath>

#include <ctime>

#include <iostream>

#include <algorithm>

#include <queue>

#include <set>

#include <map>

#include <stack>

#include <string>

#include <vector>

#include <deque>

#include <list>

#include <functional>

#include <numeric>

#include <cctype>

using namespace std;

typedef long long LL;

const int MAXN = 42;

const LL MAX = 0x7fffffffffffffffLL;

int n, k;

LL data[MAXN], ans, ands[MAXN];



void dfs(int now, int step, LL num) {

    if(num < ans) {

        ans = num;

    }

    if(now == n || step == k) return ;

    if((num & ands[now]) < ans) {

        dfs(now + 1, step + 1, num & data[now]);

        dfs(now + 1, step, num);

    }

}



int main() {

#ifndef ONLINE_JUDGE

    freopen("data.in", "r", stdin);

#endif

    int T;

    scanf("%d", &T);

    for(int t = 1; t <= T; t++) {

        scanf("%d%d", &n, &k);

        for(int i = 0; i < n; i++) {

            scanf("%I64d", &data[i]);

        }

        sort(data, data + n);

        copy(data, data + n, ands);

        ands[n] = MAX;

        for(int i = n - 1; i >= 0; i--) {

            ands[i] &= ands[i + 1];

        }

        ans = data[0];

        dfs(0, 0, MAX);

        printf("Case #%d: %I64d\n", t, ans);

    }

    return 0;

}