HDU 2094 STL

#include<iostream>#include<algorithm>#include<string>#include<set>#include<stdio.h>using namespace std;int main(){int n;set<string>base;set<string>base1;char a[101],b[101];while(scanf("%d",&n),n){while(n--){scanf("%s %s",a,b);base.insert(a);base.insert(b);base1.insert(b);}if(base.size()-base1.size()==1)printf("Yes\n");elseprintf("No\n");base.clear();base1.clear();}return 0;}