P1536 村村通

https://www.luogu.com.cn/problem/P1536

#include<bits/stdc++.h>
using namespace std;
int n, m, x, y, ans;
int fa[1010];
void init(){
    for(int i=1; i<=n; i++)
        fa[i]=i;
    ans=n;
}
int find(int x){
    if(fa[x]!=x)
        fa[x]=find(fa[x]);
    return fa[x];
}
void merge(int x, int y){
    int xx=find(x);
    int yy=find(y);
    fa[xx]=yy;
}
int main()
{
    while(1){
        scanf("%d%d",&n,&m);
        if(n==0)break;
        init();
        while(m--){
            scanf("%d%d", &x, &y);
            if(find(x)!=find(y)){
                merge(x, y);
                ans--;
            }
        }
        printf("%d
",--ans);
    }
    return 0;
}