leetcode 127. Word Ladder

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题目链接：leetcode

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from collections import deque
class Solution:
    
    def getNeighbors(self,word):
        neighbors = []
        letters = 'abcdefghijklmnopqrstuvwxyz'
        for i in range(len(word)):
            for letter in letters:
                newWord = word[:i]+letter+word[i+1:]
                if newWord not in self.visitedSet and newWord in self.wordSet:
                    if newWord == self.endWord:
                        return [newWord]
                    self.visitedSet.add(newWord)
                    neighbors.append(newWord)
        return neighbors
                
    def ladderLength(self, beginWord, endWord, wordList):
        """
        :type beginWord: str
        :type endWord: str
        :type wordList: List[str]
        :rtype: int
        """
        if endWord not in wordList:return 0
        level = 1
        self.endWord = endWord
        self.visitedSet = set()
        self.wordSet = set(wordList)
        q = deque()
        q.append(beginWord)
        q.append('Level')
        while len(q) != 0:
            word = q.popleft()
            if word == 'Level':
                level += 1
                if len(q) > 0:
                    q.append('Level')
                continue
            neighbors = self.getNeighbors(word)
            if neighbors:
                print("level={},word={},neighbors={}".format(level,word,neighbors))
                for neighbor in neighbors:
                    if neighbor == self.endWord:
                        return level+1
                    q.append(neighbor)
        return 0