1308 简单并查集

/* ***********************************************
Author        :PeterBishop
Created Time  :Sun 17 Feb 2019 22:47:11 CST
File Name     :t.cpp
Origin        :P O J  1308
************************************************ */

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <string>
#include <cmath>
#include <cstdlib>
#include <vector>
#include <queue>
#include <set>
#include <map>

using namespace std;
struct node{
    int f;
}T[10001];
void init(){
    for(int i=1;i<=10001;i++)
        T[i].f=i;
}
bool judge(int a,int b){
    if(T[b].f!=b)
        return false;
    T[b].f=a;
    return true;
}

int main()
{
    //freopen("out.txt","w",stdout);
    //freopen("in.txt","r",stdin);
    int k=0;
    int a,b;
    bool flag;
    while(cin>>a>>b){
        if(a<0)
            break;
        k++;
        init();
        int c,d;
        flag=judge(a,b);
        while(cin>>c>>d){
            if(c==0&&d==0)
                break;
            flag=judge(c,d);
            if(!flag){
                while(cin>>c>>d)
                    if(c==0)
                        break;
                break;
            }
        }
        if((c==0)|!flag){
            if(flag)
                cout<<"Case "<<k<<" is a tree."<<endl;
            else    
                cout<<"Case "<<k<<" is not a tree."<<endl;
        }    
    }
    return 0;
}