[HIHO1353]满减优惠（状压，枚举）

题目链接：http://hihocoder.com/problemset/problem/1353

状压枚举

#include <bits/stdc++.h>
using namespace std;

const int maxn = 110;
int n, x, s;
int a[maxn];

int main() {
    // freopen("in", "r", stdin);
    while(~scanf("%d%d",&n,&x)) {
        s = 0;
        for(int i = 1; i <= n; i++) {
            scanf("%d", &a[i]);
            s += a[i];
        }
        int ret = 0x7f7f7f7f;
        if(s < x) puts("-1");
        else {
            int nn = 1 << n;
            for(int i = 0; i < nn; i++) {
                int t = 0;
                for(int j = 0; j < n; j++) {
                    if((1 << j) & i) t += a[j+1];
                }
                if(t >= x) ret = min(ret, t);
            }
            printf("%d
", ret);
        }
    }
    return 0;
}