<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=;int W=;char ch=;
    while(!isdigit(ch))W|=ch=='-',ch=getchar();
    while(isdigit(ch))X=(X<<)+(X<<)+(ch^),ch=getchar();
    X=W?-X:X;return;
}
 
int K,n,maxn,need[];
double ans=,p[],dp[][<<];
int main()
{
    read(K),read(n);
    maxn=(<<n)-;
    for(rint i=;i<=n;++i)
    {
        scanf("%lf",&p[i]);
        while()
        {
            int x;
            read(x);
            if(!x)break;
            need[i]=need[i]|(<<x-);
        }
    }
 
    for(rint i=K;i>;--i)
    {
        for(rint s=;s<=maxn;++s)//枚举状态
        {
            for(rint j=;j<=n;++j)//枚举可能的物品种类
            {
                if((s&need[j])!=need[j]) {dp[i][s]+=dp[i+][s];continue;}
                dp[i][s]+=max(dp[i+][s],dp[i+][s|(<<j-)]+p[j]);
            }
            dp[i][s]/=n;
        }
    }
    printf("%.6lf\n",dp[][]);
return ;
}