class Solution {

public:

    int ladderLength(string beginWord, string endWord, vector<string>& wordList) {

        unordered_set<string> wordset(wordList.begin(),wordList.end());

        wordset.erase(beginWord);

        int res = ;

        queue<string> que{{beginWord}};

        while(!que.empty()){

            int len = que.size();

            for(int i=;i < len;i++){//坑：int i=0;i < que.size();i++  que.size()会不停改变

                string word = que.front(); que.pop();

                if(word == endWord) return res+;

                for(int i=;i < word.size();i++){

                    string newword = word;

                    for(char ch = 'a';ch <= 'z';ch++){

                        newword[i] = ch;

                        if(wordset.count(newword)){

                            que.push(newword);

                            wordset.erase(newword);

                        }

                    }

                }

            }

            res++;

        }

        return ;  //没找到

    }

};