并查集求连通分量的个数

题目连接：http://acm.hdu.edu.cn/diy/contest_showproblem.php?cid=23144&pid=1001

简单的并查集题目,先做一次并查集，然后如果f[x] == x那么联通分量数目加1

代码如下：

#include<iostream>
#include<algorithm>
#include<string>
#include<stack>
#include<queue>
#include<set>
#include<map>
#include<stdio.h>
#include<stdlib.h>
#include<ctype.h>
#include<time.h>
#include<math.h>

#define N 1005
#define eps 1e-9
#define pi acos(-1.0)
#define P system("pause")
using namespace std;
int f[N];
int find(int x)
{
    return x == f[x] ? x : f[x] = find(f[x]);    
}
int main()
{
//freopen("input.txt","r",stdin);
//freopen("output.txt","w",stdout);
    int n,m;
    while(scanf("%d",&n) && n)
    {
         scanf("%d",&m);
         int i;
         int x,y;
         for(i = 0; i <= n; i++)
               f[i] = i;
         for(i = 0; i < m; i++)
         {
               scanf("%d%d",&x,&y);
               x = find(x);
               y = find(y);
               if(x != y) f[x] = y;      
         }                         
         int ans = 0;
         for(i = 1; i <= n; i++)
        // {cout<<f[i]<<" ";
                 if(f[i] == i)
                      ans++;
         //}cout<<endl;
         printf("%d\n",ans-1);          
    }                                        

  //  P;                               
    return 0;    
}