1003 - Drunk - LightOJ

#include <bits/stdc++.h>
#define sf scanf
#define pf printf
#define WHITE 0
#define GRAY 1
#define BLACK 2
#define newl '\n'
#define FAST ios_base::sync_with_stdio(0);
using namespace std;
map<string , int>visited;
map<string, vector<string> >mp;
bool cycle;

void visit(string start){
  visited[start] = GRAY;
  for(int i=0; i<mp[start].size(); i++){
    if(visited[mp[start][i]] == WHITE){
      visit(mp[start][i]);
    }else if(visited[mp[start][i]] == GRAY){
      cycle = true;
      return;
    }
  }
  visited[start] = BLACK;
}

void DFS(){
  map<string, vector<string> >::iterator it;
  visited.clear();
  for(it = mp.begin() ; it!=mp.end(); it++){
    if(cycle)return;
    if(visited[(*it).first] == WHITE){
      visit((*it).first);
    }
  }
}
int main()
{
    FAST;
    int t , kase=0;
    cin >> t;
    while(t--){
      int n;
      cin >> n;
      for(int i=0; i<n; i++){
        string a , b;
        cin >> a >> b;
        mp[a].push_back(b);
        visited[a] = WHITE;
      }
      cycle = false;
      DFS();
      if(cycle)cout<<"Case "<<++kase<<": No"<<newl;
      else cout<<"Case "<<++kase<<": Yes"<<newl;
      mp.clear();
      visited.clear();
    } 

    return 0;
}