python中使用单链表实现队列的AttributeError

Question

我想用单链表实现一个队列。当我运行下面的代码时，我收到了 AttributeError。我不知道该怎么做才能解决这个问题。我假设链表的第一个作为队列的前面，而那个作为队列的后面。通过使用 while 循环，我想连接整个单链表。

class Node:
    def __init__(self, value):
        self.info = value
        self.link = None


class Queue:
    def __init__(self):
        self.front = None


    def enqueue(self, data):
        temp = Node(data)
        p = self.front
        if self.front is None:
            self.front = temp

        while p.link is not None:
            p = p.link
        p.link = temp
        temp.link = None

    def dequeue(self):
        self.front = self.front.link

    def size(self):
        p = self.start
        n = 0
        while p is not None:
            p = p.link
            n += 1
        return n

    def display(self):
        p = self.start
        while p is not None:
            p = p.link
        print(p.info, '', end='')

qu = Queue()

for i in range(4):
    add = int(input("please enter the elements "))
    qu.enqueue(add)
    qu.display()

for i in range(2):
    qu.dequeue()
    qu.display()

Traceback (most recent call last):
  File "C:/Users/HP/Music/Queue_SLList.py", line 43, in <module>
    qu.enqueue(add)
  File "C:/Users/HP/Music/Queue_SLList.py", line 18, in enqueue
    while p.link is not None:
AttributeError: 'NoneType' object has no attribute 'link'

Answer 1

当队列为空时，您在 p = self.front 时将 p 设置为 None。然后当您尝试执行 while p.link is not None 时会出现错误，因为 p 不是节点。

如果您要对第一个 noe 进行排队，您应该 return 从该方法中。

    def enqueue(self, data):
        temp = Node(data)
        if self.front is None:
            self.front = temp
            return

        p = self.front
        while p.link is not None:
            p = p.link
        p.link = temp
        temp.link = None

python中使用单链表实现队列的AttributeError

AttributeError in the implementation of queue by using Single Linked List in the python

python

queue

singly-linked-list

enqueue