Leetcode 127.cpp

class Solution {
private:
    // bool differby1(string s,string &s1){
    //     int count=0;
    //     for(int i=0;i<s.size();i++){
    //         if(s[i]!=s1[i])count++;
    //     }
    //     if(count==1)return true;
    //     return false;

    // }
public:
    int ladderLength(string beginWord, string endWord, vector<string>& wordList) {
        
        queue<pair<string,int>>q;
         q.push({beginWord,1});
         unordered_set<string>s(wordList.begin(),wordList.end());
         s.erase(beginWord);

         while(!q.empty()){
             string word = q.front().first;
             int steps = q.front().second;
             q.pop();
             if(word == endWord)return steps;

             for(int i=0;i<word.size();i++){
                 char original = word[i];
                 for(char ch ='a';ch<='z';ch++){
                     word[i]=ch;
                     if(s.find(word)!=s.end()){
                         s.erase(word);
                         q.push({word,steps+1});
                     }
                 }
                 word[i]=original;
             }


         }

        return 0;
    }
};