bzoj1076: [SCOI2008]奖励关

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int maxn = 20;
const int maxm = 1<<16;
const int maxk = 100 + 10;

int n,m,k;
int pre[maxn];
int p[maxn];
double f[maxk][maxm];

int main() {
    scanf("%d%d",&k,&n); m=(1<<n)-1;
    for(int i=1,t;i<=n;i++) {
        scanf("%d",&p[i]);
        while(scanf("%d",&t) && t) 
            pre[i]|=1<<(t-1);
    }
    
    for(int i=k-1;i>=0;i--) {
        for(int s=0;s<=m;s++) {
            for(int j=1;j<=n;j++) 
                if((s&pre[j])==pre[j]) f[i][s]+=max(f[i+1][s],f[i+1][s|(1<<(j-1))]+p[j]);
                else f[i][s]+=f[i+1][s];
            f[i][s]/=n;
        }
    }
    printf("%.6lf\n",f[0][0]);
    return 0;
}