CCCC L2 部落 L3社交集群

https://www.patest.cn/contests/gplt/L2-024

题解：部落是并查集模板题。

　　　　社交集群用并查集暴力有23分

坑:写了半天，发现自己并查集没怎么学明白，现在才搞懂；

　　find :return f[x]=find(f[x]);

　　询问：if(find(x)==find(y))

　　合并：xx=find(x),yy=find(y);f[xx]=yy;

#include<iostream>
#include<algorithm>
#include<stdio.h>
#include<string>
#include<map>
#include<vector>
#define _for(i, a, b) for (int i = (a); i<(b); ++i)
using namespace std;
typedef long long ll;
const int N = 1e4 + 5;
int f[N];
int find(int x) {
    return f[x] == x ? x : f[x] = find(f[x]);
};
void un(int x, int y) {
    int xx = find(x);
    int yy = find(y);
     f[xx]= yy ;
};
int main() {
    int n;
    int mn = 0;
    cin >> n;
    _for(i, 0, N) f[i] = i;
    while (n--) {
        int x;
        cin >> x;
        int y1; cin >> y1; mn = max(mn, y1);
        _for(i, 0, x - 1)
        {
            int y;
            cin >> y; mn = max(mn, y);
            un(y1, y);
        }
    }
    int cnt = 0;
    _for(i, 0, mn) {
        if (f[i+1] == i+1)cnt++;
    }
    cout << mn << ' ' << cnt << endl;
    int q;
    cin >> q;
    while (q--) {
        int x, y;
        cin >> x >> y;
        if (find(x) == find(y))cout << "Y" << endl;
        else cout << "N" << endl;
    }

}