poj 2524 Ubiquitous Religions

Description

Input

Output

Sample Input

10 9
1 2
1 3
1 4
1 5
1 6
1 7
1 8
1 9
1 10
10 4
2 3
4 5
4 8
5 8
0 0

Sample Output

Case 1: 1
Case 2: 7

一道并查集基础题！

贴出两段代码！
求解释？为什么第二段代码的时间有一千多毫秒！

#include <iostream>
const int MAX = 50001;
int p[MAX],rank[MAX];
int result;

int findSet(int x)
{
	if(x!=p[x])
		p[x] = findSet(p[x]);
	return p[x];
}

void Union(int x, int y)
{
	if(x == y)
		return;
	result--;
	if(rank[x] > rank[y])
	{
		p[y] = x;
	}
	else
	{
		p[x] = y;
		if(rank[x] == rank[y])
			rank[y]++;
	}
}

int main()
{
	int i,j;
	int s1,s2;
	int x,y;
	int n,m;
	int t = 1;
	while(true)
	{
		scanf("%d %d",&n,&m);
		if(n==0&&m==0) break;
		result = n;
		for(i = 1; i <= n; i++)
		{
			p[i] = i;
			rank[i] = 0;
		}
		for(i = 1; i <= m; i++)
		{
			scanf("%d %d",&x,&y);
			s1 = findSet(x);
			s2 = findSet(y);
			Union(s1,s2);
		}
		printf("Case %d: ",t++);
		printf("%d\n",result);
	}
	return 0;
}
<pre name="code" class="html">#include<iostream>
using namespace std;
const int MAX =50001;
int father[MAX],rank[MAX];
int result;
int Find_Set(int x)
{
	if(x!=father[x])
		father[x]=Find_Set(father[x]);
	return father[x];
}
void Union_Set(int x,int y)
{

	if(x==y)return ;
	result--;
	if(rank[x]>rank[y])
	{
		father[y]=x;
	}
	else 
	{
		father[x]=y;
		if(rank[x]==rank[y])
			rank[y]++;
	}
}
int main()
{
	int n,m;
	int i,x,y,s1,s2;
	int num=1;
	while(true)
	{
		cin>>n>>m;	
		if(n==0&&m==0)break;
		result = n;
		for(i=1;i<=n;i++)
		{
			father[i]=i;
			rank[i]=0;
		}
		for(i=1;i<=m;i++)
		{
			cin>>x>>y;	
			s1=Find_Set(x);
	        s2=Find_Set(y);
			Union_Set(s1,s2);
		}
			cout<<"Case "<<num++<<": "<<result<<endl;
	}
	return 0;
}