class Solution(object):
    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
        queue = []
        queue.append((beginWord, 1))
        visited = set()
        while len(queue)>0:
            currword, currlvl = queue.pop(0)
            if currword == endWord:
                return currlvl
            for word in wordList:
                if word not in visited:
                    if self.checkifonediff(currword, word):
                        visited.add(word)
                        queue.append((word, currlvl + 1))
        return 0

    def checkifonediff(self, cword, word):
        count = 0
        for i in range(len(cword)):
            if cword[i] != word[i]:
                count += 1
        if count != 1:
            return False
        return True