<SCOI2008>奖励关

emmm第一道期望dp+个状压

真有趣..

#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
#define max(a,b) (a>b?a:b)
#define rint register int
template <class T>inline void read(T &X)
{
    X=0;int W=0;char ch=0;
    while(!isdigit(ch))W|=ch=='-',ch=getchar();
    while(isdigit(ch))X=(X<<3)+(X<<1)+(ch^48),ch=getchar();
    X=W?-X:X;return;
}

int K,n,maxn,need[55];
double ans=0,p[20],dp[55][1<<16];
int main()
{
    read(K),read(n);
    maxn=(1<<n)-1;
    for(rint i=1;i<=n;++i)
    {
        scanf("%lf",&p[i]);
        while(1)
        {
            int x;
            read(x);
            if(!x)break;
            need[i]=need[i]|(1<<x-1);
        }
    }
    
    for(rint i=K;i>0;--i)
    {
        for(rint s=0;s<=maxn;++s)//枚举状态 
        {
            for(rint j=1;j<=n;++j)//枚举可能的物品种类 
            {
                if((s&need[j])!=need[j]) {dp[i][s]+=dp[i+1][s];continue;}
                dp[i][s]+=max(dp[i+1][s],dp[i+1][s|(1<<j-1)]+p[j]);
            }
            dp[i][s]/=n;
        }
    }
    printf("%.6lf\n",dp[1][0]);
return 0;
}