leetcode——127—— Word Ladder

Given two words (beginWord and endWord), and a dictionary's word list, find the length of shortest transformation sequence frombeginWord to endWord, such that:

1. Only one letter can be changed at a time
2. Each intermediate word must exist in the word list

For example,

Given:
beginWord = "hit"
endWord = "cog"
wordList = ["hot","dot","dog","lot","log"]

As one shortest transformation is "hit" -> "hot" -> "dot" -> "dog" -> "cog",
return its length 5.

Note:

• Return 0 if there is no such transformation sequence.
• All words have the same length.
• All words contain only lowercase alphabetic characters.

class Solution {public:    int ladderLength(string beginWord, string endWord, unordered_set<string>& wordList) {       if(beginWord == endWord || beginWord.size() != endWord.size())            return 0;                    queue<string> que;        que.push(beginWord);        que.push("");        int height = 0;        int len = beginWord.size();        while(true) {            string word = que.front();            que.pop();            if(que.empty())break;            if(word == "") {                height++;                que.push("");                continue;            }            else if(word == endWord) {                return height + 1;            }            for(auto i = 0; i < len; i++) {                for(auto j = 'a'; j <= 'z'; j++) {                    char l = word[i];                    word[i] = j;                    if(wordList.find(word) == wordList.end()){                        word[i] =l;                        continue;                    }                    que.push(word);                    wordList.erase(word);                    word[i] =l;                }            }        }        return 0;     }};