POJ2524 Ubiquitous Religions

 1 #include<iostream>
 2 #include<cstring>
 3 #include<cstdio>
 4 using namespace std;
 5 const int maxn=50005;
 6 int t,n,m,ans,f[maxn],cnt[maxn];
 7 int fnd(int x)
 8 {
 9     if(f[x]!=x)
10         f[x]=fnd(f[x]);
11     return f[x];
12 }
13 int main()
14 {
15     while(scanf("%d%d",&n,&m)&&(n||m))
16     {
17         ans=n;
18         for(int i=1;i<=n;i++)
19             f[i]=i;
20         int x,y;
21         while(m--)
22         {
23             scanf("%d%d",&x,&y);
24             if(fnd(x)!=fnd(y))
25             {
26                 f[fnd(y)]=fnd(x);
27                 ans--;
28             }
29         }
30         printf("Case %d: %d\n",++t,ans);
31     }
32     return 0;
33 }