#include<iostream>
using namespace std;
int main()
{	int tree[15],treef[15],a,b,c,node,cas=1,tag;	
	while(cin>>a>>b&&(a!=-1||b!=-1))
	{
		if(a==0&&b==0)
			cout<<"Case "<<cas<<" is a tree."<<endl;
		else
		{	node=tag=1;
			if(a==b)
			tag=0;			
			memset(tree,0,15*sizeof(int));
			memset(treef,0,15*sizeof(int));
			tree[b]++;
			treef[a]++;
			treef[b]++;
			while(cin>>a>>b&&(a||b))
			{tree[b]++;treef[a]++;treef[b]++;node++;
			if(a==b)
			tag=0;}
			b=c=0;
			for(a=0;a<15;a++)
			{if(tree[a]>=2)
					tag=0;
			b+=tree[a];
			if(treef[a]!=0&&tree[a]==0)
			c++;}
				if(b!=node)
					tag=0;
				if(c!=1)
					tag=0;
			if(tag)
				cout<<"Case "<<cas<<" is a tree."<<endl;
			else
				cout<<"Case "<<cas<<" is not a tree."<<endl;
		}
		cas++;
	}
return 0;}

• Re:200，留念，挫代码，我也贴 (883) pirates 2012-07-23 00:33:10