HDU5036 Explosion(期望&&bitset)

#include <iostream>
#include <cstring>
#include <string>
#include <vector>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <bitset>
using namespace std;

#define maxn 1005

bitset<1100> b[maxn];
int n;

int main()
{
    int T;cin>>T;int ca=0;
    while(T--){
        scanf("%d",&n);
        for(int i=1;i<=n;++i) b[i].reset();
        for(int i=1;i<=n;++i){
            int num;scanf("%d",&num);
            b[i][i]=true;
            while(num--){
                int tmp;
                scanf("%d",&tmp);
                b[i][tmp]=true;
            }
        }
        for(int i=1;i<=n;++i){
            for(int j=1;j<=n;++j){
                if(b[j][i]) b[j]|=b[i];
            }
        }
        double ans=0;
        for(int i=1;i<=n;++i){
            int cnt=0;
            for(int j=1;j<=n;++j){
                if(b[j][i]) ++cnt;
            }
            ans+=1.0/cnt;
        }
        printf("Case #%d: %.5lf\n",++ca,ans);
    }
    return 0;
}