Problem

As the leader of the Evil League of Evil, Bad Horse has a lot of problems to deal with. Most recently, there have been far too many arguments and far too much backstabbing in the League, so much so that Bad Horse has decided to split the league into two departments in order to separate troublesome members. Being the Thoroughbred of Sin, Bad Horse isn't about to spend his valuable time figuring out how to split the League members by himself. That what he's got you -- his loyal henchman -- for.

Input

The first line of the input gives the number of test cases, T. T test cases follow. Each test case starts with a positive integer M on a line by itself -- the number of troublesome pairs of League members. The next M lines each contain a pair of names, separated by a single space.

Output

For each test case, output one line containing "Case #x: y", where x is the case number (starting from 1) and y is either "Yes" or "No", depending on whether the League members mentioned in the input can be split into two groups with neither of the groups containing a troublesome pair.

Limits

1 ≤ T ≤ 100.
Each member name will consist of only letters and the underscore character.
Names are case-sensitive.
No pair will appear more than once in the same test case.
Each pair will contain two distinct League members.

Small dataset

1 ≤ M ≤ 10.

Large dataset

1 ≤ M ≤ 100.

Sample

推薦指數：※※※

來源：google

可以轉換成典型的判斷是否是二分圖問題。

BFS採用圖著色。如果兩個顏色可以，這是二分圖，否則不是。

注意多個不連通子圖的情況

#include<iostream>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<map>
#include<queue>
#include<string>
using namespace std;
const int T=201;
int    color[T],visited[T];
int bfs(int index,vector<vector<int> > *adj,int n){
	int i,j;
	memset(color,-1,sizeof(color));
	memset(visited,0,sizeof(visited));
	queue<int >q;
	q.push(index);
	visited[index]=true;
	color[index]=0;
	while(!q.empty()){
		int tmp_now=q.front();
		for(i=0;i<(*adj)[tmp_now].size();i++){
			int tmp_index=(*adj)[tmp_now][i];
			if(color[tmp_index]==-1){
				color[tmp_index]=(color[tmp_now]+1)%2;
				q.push(tmp_index);
				visited[tmp_index]=true;
			}
			else if(color[tmp_index]==color[tmp_now]&&tmp_index!=tmp_now)//color is same and is a new node
				return false;
		}
		q.pop();
	}
	for(i=0;i<n;i++){
		if(visited[i]==false){
			return bfs(i,adj,n);
		}
	}
	return true;
}
int main()
{
	freopen("a.in", "r", stdin);
   freopen("a.out", "w", stdout);
	int loops;
	scanf("%d",&loops);
	int casenum;
	for(casenum=1;casenum<=loops;casenum++){
		int pairs,i;
		scanf("%d",&pairs);
		vector<vector<int> >adj;
		adj.resize(T);
		map<string,int> mp;
		int m_id=0;
		for(i=0;i<pairs;i++){
			string a,b;
			int tmp_a,tmp_b;
			cin>>a>>b;
			if(mp.count(a)>0){//hash
				tmp_a=mp[a];
			}
			else{
				mp[a]=m_id;
				tmp_a=m_id;
				m_id++;
			}
			if(mp.count(b)>0){//hash 
				tmp_b=mp[b];
			}
			else{
				mp[b]=m_id;
				tmp_b=m_id;
				m_id++;
			}
			adj[tmp_a].push_back(tmp_b);
			adj[tmp_b].push_back(tmp_a);
		}
		if(bfs(0,&adj,m_id)==true)
			printf("Case #%d: Yes\n",casenum);
		else
			printf("Case #%d: No\n",casenum);
	}
	return 0;
}