#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
using namespace std;
int f[1005];
int main()
{
    int a,b,ca(1),k,i;
    while(scanf("%d%d",&a,&b),a!=-1||b!=-1)
    {
        int flag=0;
        memset(f,-1,sizeof(f));
        if(a==0&&b==0) { printf("Case %d is a tree.\n",ca++);continue;}
        //空树
        if(a==b) flag=1;//指向自己
        f[b]=f[a]=a;
        int c,d,k=2;
        while(scanf("%d%d",&c,&d),c||d)
        {
            if(f[c]==-1)k++;
            if(f[d]==-1)k++;
            if(c==d||f[d]!=d&&f[d]!=-1||f[c]==c&&f[d]==c)flag=1;
            //判重，成环
            f[d]=f[c]=c;
        }
        if(flag){printf("Case %d is not a tree.\n",ca++);continue;}
        int ans=0;
        for(i=0;i<k;i++)
        if(f[i]==i)ans++;//森林
        if(ans==1)printf("Case %d is a tree.\n",ca++);
        else printf("Case %d is not a tree.\n",ca++);
    }


 return 0;
}

• Re:大牛求指点，数据都过了，wa的好辛苦 (1035) 1004101213 2011-10-31 12:55:22
  • Re:大牛求指点，数据都过了，wa的好辛苦 (962) 1004101213 2011-10-31 15:17:01