hdu 1232 并查集

#include <iostream>
using namespace std;

#define MAX 10001
int N,M;

int Father[MAX];
int Rank[MAX];
int sum;


void Make_Set(int x)
{
	Father[x] = x;	
	Rank[x] = 1;
}

int Find(int x)
{
	while(x != Father[x])
	{
		x = Father[x];
	}
	return x;
}


void Union(int x,int y)
{
	x = Find(x);
	y = Find(y);
	if(x == y)
		return;
	if(Rank[x] > Rank[y])
	{
		Father[y] = x;
		Rank[x] += Rank[y];
	}
	else
	{
		Father[x] = y;
		Rank[y] += Rank[x];
	}
	sum --;
}

int main()
{
	while(cin>>N)
	{
		if(N == 0)
			break;
		sum = N;
		cin>>M;
		int x,y;
		for(int i = 0; i <= N; i++)
		{
			Make_Set(i);
		}
		for(int i = 1; i <= M; i++)
		{
			cin>>x>>y;
			Union(x,y);
		}
		cout<<sum-1<<endl;
	}

	return 0;
}