并查集 ---- 啊哈算法

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//
// Created by jal on 18-9-3.
//

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 100;
int n,m;
int F[MAXN];

int father(int u){
    return F[u] == u ? u : F[u] = father(F[u]);
}
void merge(int u, int v){
    int root_u = father(u);
    int root_v = father(v);
    if(root_u != root_v){
        F[root_u] = root_v;
    }
}
int main(){
    cin >> n >> m;
    for(int i = 1; i <= n; i++){
        F[i] = i;
    }
    for(int i = 1; i <= m; i++){
        int x,y,z;
        cin >> x >> y;
        merge(x,y);
    }
    int cnt = 0;
    for(int i = 1; i <= n; i++){
        if(F[i] == i){
            cnt++;
        }
    }
    cout << cnt << endl;
}

/*
 input:

 10 9
 1 2
 3 4
 5 2
 4 6
 2 6
 8 7
 9 7
 1 6
 2 4

 output:

 3
 */