【传递闭包】 HDOJ 5036 Explosion

#include <iostream>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <bitset>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 1005
#define maxm 300005
#define eps 1e-10
#define mod 10000007
#define INF 1e17
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid
#define rson o<<1 | 1, mid+1, R
typedef long long LL;
//typedef int LL;
using namespace std;
LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}
LL gcd(LL _a, LL _b){if(!_b) return _a;else return gcd(_b, _a%_b);}
//head

bitset<maxn> p[maxn];
int n, m;

void read(void)
{
scanf("%d", &n);
for(int i = 1; i <= n; i++) {
p[i].reset();
p[i][i] = true;
}
for(int i = 1; i <= n; i++) {
scanf("%d", &m);
while(m--) {
int j;
scanf("%d", &j);
p[i][j] = true;
}
}
}
void work(int _)
{
for(int i = 1; i <= n; i++)
for(int j = 1; j <= n; j++)
if(p[j][i]) p[j] |= p[i];
double ans = 0;
for(int i = 1; i <= n; i++) {
int cnt = 0;
for(int j = 1; j <= n; j++)
if(p[j][i]) cnt++;
ans += 1.0 / cnt;
}
printf("Case #%d: %.5f\n", _, ans);
}
int main(void)
{
int _, __;
while(scanf("%d", &_)!=EOF) {
__ = 0;
while(_--) {
read();
work(++__);
}
}
return 0;
}