村村通（并查集模板）

就是模板题：

#include<iostream>
using namespace std;

const int maxn = 1e3 + 10;
int fa[maxn];

int getfa(int x){
    if (fa[x] == x)return x;
    return fa[x] = getfa(fa[x]);
}

int find(int x, int y){
    return getfa(x) == getfa(y);
}

void H_(int x, int y){
    if (!find(x, y))fa[getfa(x)] = fa[getfa(y)];
}
int n, m, x, y, ans;

int main(){
    while (cin >> n >> m){
        ans = n - 1;
        for (int i = 1; i <= n; ++i)
            fa[i] = i;
        for (int i = 1; i <= m; ++i)
        {
            cin >> x >> y;
            if (find(x, y))continue;
            H_(x, y);
            ans--;
        }
        cout << ans << endl;
    }
}