p2835 并查集 + floyd

/*************************************************************************
    > File Name: p2835.cpp
    > Author: Ansary
    > Created Time: 2022/3/13 11:06:12
 ************************************************************************/

#include <iostream>
#include <cstring>
#include <algorithm>
#include <vector>
#include <string>

using namespace std;

int pre[300];
int vis[300][300];
int sum = 0;

int find(int x){
    if(pre[x] == x)
        return x;
    return pre[x] = find(pre[x]);
}

void merge(int x, int y){
    int fx = find(x);
    if(fx == y)
        return;
    pre[y] = fx; 
}

int main(){
    int n;
    cin >> n;
    for(int i = 1; i <= n; i++)
        pre[i] = i;

    for(int i = 1; i <= n; i++){
        int t;
        cin >> t;
        while(t != 0){
            vis[i][t] = 1;
            cin >> t;
        }
    }

    for(int k = 1; k <= n; k++)
        for(int i = 1; i <= n; i++)
            for(int j = 1; j <= n; j++)
                vis[i][j] = vis[i][j] || (vis[i][k] && vis[k][j]);
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= n; j++)
            if(vis[i][j])
                merge(i, j);        
    for(int i = 1; i <= n; i++)
        if(pre[i] == i)
            sum++;
    cout << sum << endl;
}