POJ2524 Ubiquitous Religions —— 并查集

#include<iostream>//B - Ubiquitous Religions POJ - 2524   纯并查集
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<algorithm>
#include<map>
#define LL long long
using namespace std;

int fa[50005];

int find(int x)
{
return (fa[x]==x?x:find(fa[x]));
}

int main()
{
int n,m,a,b,ans,t = 0;

while(scanf("%d%d",&n,&m) && (n||m))
{
for(int i = 1; i<=n; i++)
fa[i] = i;

for(int i = 0; i<m; i++)
{
scanf("%d%d",&a,&b);
a = find(a);
b = find(b);
if(a!=b)
fa[a] = b;
}

ans = 0;
for(int i = 1; i<=n; i++)
if(fa[i]==i) ans++;

printf("Case %d: %d\n",++t,ans);
}
}