简单求解集合数即可

#include <bits/stdc++.h>
using namespace std;
int n,m,q,fa[5010];
int find(int x){
	if (x!=fa[x])fa[x]=find(fa[x]);
	return fa[x];
}
void merge(int x,int y){
	int tx=find(x);
	int ty=find(y);
	if (tx!=ty)fa[tx]=ty;
}
int main(){
	while (true){
		cin>>n;
		if (n==0)break;
		cin>>m;
		for (int i=1;i<=n;i++)fa[i]=i;
		int x,y;
		for (int i=1;i<=m;i++){
			cin>>x>>y;
			merge(x,y);
		}
		int c=0;
		for (int i=1;i<=n;i++){
			if (fa[i]==i)c++;
		}
		cout<<c-1<<endl;//要-1
	}
	return 0;
}