> #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 (962) 1004101213 2011-10-31 15:17:01