并查集入门题
#include<bits/stdc++.h> using namespace std; int father[1005]; void f(int x,int y) { while(x!=father[x]) x=father[father[x]]; while(y!=father[y]) y=father[father[y]]; if(x!=y) father[x]=y; } int main() { int n,m,a,b; while(scanf("%d",&n)==1&&n) { scanf("%d",&m); for(int i=1;i<=n;i++) father[i]=i; while(m--) { scanf("%d%d",&a,&b); if(a==b) continue; f(a,b); } int ans=0; for(int i=1;i<=n;i++) if(i==father[i]) ans++; printf("%d\n",ans-1); } return 0; }