給定此代碼...import Queuedef breadthFirstSearch(graph, start, end):q = Queue.Queue()path = [start]q.put(path)visited = set([start])while not q.empty():    path = q.get()    last_node = path[-1]    if last_node == end:        return path    for node in graph[last_node]:        if node not in visited:            visited.add(node)            q.put(path + [node])其中g(shù)raph是代表有向圖的字典，例如{'stack'：['overflow']，'foo'：['bar']}，即，堆棧指向溢出，而foo指向bar。為什么將queque.Queue替換為來自集合的雙端隊列以提高效率，為什么我沒有得到相同的結(jié)果？from collections import dequedef breadthFirstSearch(graph, start, end):q = deque()path = [start]q.append(path)visited = set([start])while q:    path = q.pop()    last_node = path[-1]    if last_node == end:        return path    for node in graph[last_node]:        if node not in visited:            visited.add(node)            q.append(path + [node])