Word ladder

class Solution {
public:
    int ladderLength(string beginWord, string endWord, vector<string>& wordList) {
          queue < pair <string , int> > q  ;
          map < string , int > m ; 
          for(int i = 0 ; i < wordList.size() ; i++)
          {
              m[wordList[i]]++ ; 
          } 
          int n = endWord.size() ; 
          q.push({beginWord , 1}) ; 
          
          while(!q.empty())
          {
              
              string word = q.front().first; 

              int dis = q.front().second ;
              q.pop() ; 
              string x = word ; 
              for(int currind = 0 ; currind  <  n ; currind++)
              {
                for(int i = 'a' ; i <= 'z'; i++)
                {
                    x[currind] = i ; 
                    
                    if( m.count(x) > 0 && m[x] != -1 )
                    {
                        if(x == endWord)
                    {
                        return dis + 1 ; 
                    }
                        q.push({x , dis +  1 }) ; 
                        m[x] = -1 ; 
                    } 
                    x = word ; 
                }
              }

          }
          return 0 ; 

    }
};