循环队列Python

Question

我试图在Python中创建一个循环队列,以便当数组中的最后一个元素到达指向头部时.我正在研究入队方法,我遇到了一些问题.我正在尝试使用大小为4的数组,并且我能够将值排到第4位,但是当它执行elif语句时,我收到此错误.

TypeError:+的不支持的操作数类型:'Node'和'int'

有什么想法吗？

class Node(object):
    def __init__(self, item = None):
        self.item = [None] * 4
        self.next = None
        self.previous = None

class CircularQueue(object):
    def __init__(self):
        self.length = 0
        self.head = None
        self.tail = None
    def enqueue(self, x):
        newNode = Node(x)
        newNode.next = None
        if self.head == None:
            self.head = newNode
            self.tail = newNode
        elif self.length < 4:
            self.tail.next = newNode
            newNode.previous = self.tail
            self.tail = newNode
        else:
            self.tail = (self.tail + 1) % 4
        self.length += 1
    def dequeue(self):
        if self.count == 0:
            print ("The Queue is empty!")
        self.count -= 1
        return self.item.pop()
    def size(self):
        return self.length

Answer 1

如果您不必自己实现,可以使用标准库 deque

from collections import deque

circular_queue = deque([1,2], maxlen=4)
circular_queue.append(3)
circular_queue.extend([4])

# at this point you have [1,2,3,4]
print(circular_queue.pop())  # [1,2,3] --> 4

# key step. effectively rotate the pointer
circular_queue.rotate(-1)  # negative to the left. positive to the right

# at this point you have [2,3,1]
print(circular_queue.pop())  # [2,3] --> 1