poj 2524（并查集）

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
#define MAXN 100000
int father[MAXN],used[MAXN];
void make_set(int x)
{
    father[x]=x;
}
int find_set(int x)
{
    if(x==father[x])
        return x;
    else return father[x]=find_set(father[x]);
}
void union_set(int x,int y)
{
    int rx=find_set(x);
    int ry=find_set(y);
    father[rx]=ry;
}
int main()
{
    int i,n,m,CASE=0;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        if(n==0&&m==0) return 0;
        for(i=1;i<=n;i++)
            make_set(i);
        while(m--)
        {
            int a,b;
            scanf("%d%d",&a,&b);
            int ra=find_set(a);
            int rb=find_set(b);
            if(ra!=rb)
                union_set(a,b);
        }
        int ans=0;
        memset(used,0,sizeof(used));
        for(i=1;i<=n;i++)
        {
            int ri=find_set(i);
            if(used[ri]==0)
            {
               used[ri]=1;
               ans++;
            }
        }
        printf("Case %d: %d\n",++CASE,ans);
    }
}