E - 产生冠军 HDU - 2094

AC代码

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n;
	while(cin>>n && n)
	{
		set<string> a,b;
		string s1,s2;
		while(n--)
		{
			cin>>s1>>s2;
			a.insert(s1);
			a.insert(s2);
			b.insert(s2);
		}
		if( (a.size()-b.size()) ==1) cout<<"Yes\n";
		else cout<<"No\n";
	}
	return 0;
}