word ladder

def get_next_word(self, bfs_queue, head, dict, end, set_visit):
        for i in range(len(head)):
            temp = ""
            for j in range(97, 97+26):
                if j != ord(head[i]):
                    temp = head[:i] + chr(j) + head[i+1:]
                    if temp not in set_visit and (temp in dict or temp == end):
                        bfs_queue.append(temp)
                        set_visit.add(temp)
        return 
        
    """
    @param: start: a string
    @param: end: a string
    @param: dict: a set of string
    @return: An integer
    """
    def ladderLength(self, start, end, dict):
        # write your code here
        set_visit, bfs_queue, result = set(), [start], 1
        set_visit.add(start)
        while len(bfs_queue) > 0:
            size = len(bfs_queue)
            for i in range(size):
                head = bfs_queue.pop(0)
                if head == end:
                    return result
                self.get_next_word(bfs_queue, head, dict, end, set_visit)
            result += 1