1003 - Drunk

/*
Name:  Raihan Chowdhury 
   International Islamic University Chittagong 
   Email:  raihanraju02@gmail.com
   Problem: Graph (lightoj 1003)
  comment: Topological Sort test by finding cycle
  
*/
#include <bits/stdc++.h>
using namespace std;
vector<int> v[10005];
int c[100005];
bool Top_sort(int total)
{
    int ans = total;
    int cnt = 0;
    queue<int> q;
    for(int i = 1; i <= total; i++)
    {
        if(c[i] == 0)
        {
            cnt++;
            q.push(i);
        }
    }
 
    while(!q.empty())
    {
        int u = q.front();
        q.pop();
        for(int i = 0; i < v[u].size(); i++)
        {
            int vx = v[u][i];
            c[vx]--;
            if(c[vx] == 0)
            {
                cnt++;
                q.push(vx);
            }
        }
 
    }
 
    if(cnt == ans)
        return true;
    else
        return false;
}
int main()
{
    int tes , o = 0;
    cin >> tes;
 
    while(tes--)
    {
        o++;
        int q;
        cin >> q;
        string a;
        string b;
        int in = 1;
        map< string, int> mp;
        memset(c, 0, sizeof c);
        for(int i = 0; i < q; i++)
        {
            cin >> a;
            cin >> b;
            if(mp[a] == 0)
                mp[a] = in++;
            if(mp[b] == 0)
                mp[b] = in++;
 
                v[mp[a]].push_back(mp[b]);
 
           c[mp[b]]++;
        }
        bool x = Top_sort(in - 1);
 
        if(x == true)
            printf("Case %d: Yes\n",o);
        else
            printf("Case %d: No\n",o);
 
      mp.clear();
      for(int i = 1; i <= in; i++)
        v[i].clear();
 
    }
}