Alien Dictionary

string printOrder(string dict[], int N, int k)
{
   map<char,vector<char> >mp;
   map<char,int>check;
   
   for(int i=0;i<N-1;i++)
   {
        string s1=dict[i];
        string s2=dict[i+1];
       for(int i=0;i<min(s1.length(),s2.length());i++)
       {
           check[s1[i]]++;
           check[s2[i]]++;
          if(s1[i]!=s2[i])
          {
              mp[s1[i]].push_back(s2[i]);
              break;
          }
       }
   }
   
   map<char,int>indegree;
   
   for(auto x:check)
   {
       indegree[x.first]=0;
   }
   
   for(auto x:mp)
      {
          for(auto y:x.second)
          {
              indegree[y]++;
          }
      }
      
      string ans;
      
      queue<char>q;
      
      for(auto x:indegree)
         if(x.second==0)
            q.push(x.first);
           
           
    
    while(!q.empty())
    {
        char ch=q.front();
        q.pop();
         ans+=ch;
         
         for(auto x:mp[ch])
         {
             indegree[x]--;
             
             if(indegree[x]==0)
                q.push(x);
         }
    }
    
  return ans;  
    
   
}