class Solution {public:    int ladderLength(string beginWord, string endWord, vector
     
      & wordList) {        vector
      
        vis(wordList.size(),0);        int res = INT_MAX;        DFS(beginWord,endWord,wordList,res,vis);        if(res == INT_MAX) return 0;        else return res+1;    }    bool comp(string s1,string s2){        int cnt = 0;        for(int i=0;i < s1.size();i++){            if(s1[i] != s2[i]) cnt++;        }        if(cnt == 1) return true;        else return false;    }        void DFS(string beginWord, string endWord, vector
       
         wordList,int& res,vector
        
          vis){        if(beginWord == endWord){            int cnt = 0;            for(int i=0;i < vis.size();i++){                if(vis[i] == 1)cnt++;            }            res = min(res,cnt);        }        for(int i=0;i < wordList.size();i++){            if(!vis[i] && comp(beginWord,wordList[i])){                vis[i] = 1;                DFS(wordList[i],endWord,wordList,res,vis);                vis[i] = 0;            }        }    }};
        
       
      
     

_DFS写炸了，研究一下BFS