UVALive 6091 并查集简单应用

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <iostream>
#include <algorithm>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int inf=0x3f3f3f3f;
const ll INF=0x3f3f3f3f3f3f3f3fll;
const int maxn=510;
int f[maxn],num[maxn],r[maxn];
int find1(int x){
if(x!=f[x]) f[x]=find1(f[x]);
return f[x];
}
void unite(int a,int b){
int aa=find1(a);
int bb=find1(b);
if(aa==bb){
num[bb]++;return ;
}
f[aa]=bb;num[bb]+=num[aa];r[bb]+=r[aa];
}
int main(){
int n,m,u,v,cas=1;
while(scanf("%d%d",&n,&m)!=-1){
if(n==0&&m==0) break;
for(int i=0;i<=n;i++){
f[i]=i;num[i]=1;r[i]=1;
}
for(int i=0;i<m;i++){
scanf("%d%d",&u,&v);
unite(u,v);
}
int sum=0;
for(int i=1;i<=n;i++){
if(find1(i)==i){
if(r[i]==num[i]) sum++;
}
}
if(sum==0) printf("Case %d: No trees.\n",cas++);
else if(sum==1) printf("Case %d: There is one tree.\n",cas++);
else printf("Case %d: A forest of %d trees.\n",cas++,sum);
}
return 0;
}