hello-algo/codes/python/chapter_stack_and_queue/array_queue.py

"""
File: array_queue.py
Created Time: 2022-12-01
Author: Peng Chen (pengchzn@gmail.com)
"""

import os.path as osp
import sys

sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
from modules import *

class ArrayQueue:
    """ 基于环形数组实现的队列 """
    def __init__(self, size):
        """ 构造方法 """
        self.__nums = [0] * size  # 用于存储队列元素的数组
        self.__front = 0          # 队首指针，指向队首元素
        self.__size = 0           # 队列长度

    def capacity(self):
        """ 获取队列的容量 """
        return len(self.__nums)

    def size(self):
        """ 获取队列的长度 """
        return self.__size

    def is_empty(self):
        """ 判断队列是否为空 """
        return self.__size == 0

    def push(self, num):
        """ 入队 """
        assert self.__size < self.capacity(), "队列已满"
        # 计算尾指针，指向队尾索引 + 1
        # 通过取余操作，实现 rear 越过数组尾部后回到头部
        rear = (self.__front + self.__size) % self.capacity()
        # 将 num 添加至队尾
        self.__nums[rear] = num
        self.__size += 1

    def poll(self):
        """ 出队 """
        num = self.peek()
        # 队首指针向后移动一位，若越过尾部则返回到数组头部
        self.__front = (self.__front + 1) % self.capacity()
        self.__size -= 1
        return num

    def peek(self):
        """ 访问队首元素 """
        assert not self.is_empty(), "队列为空"
        return self.__nums[self.__front]

    def to_list(self):
        """ 返回列表用于打印 """
        res = [0] * self.size()
        j = self.__front
        for i in range(self.size()):
            res[i] = self.__nums[(j % self.capacity())]
            j += 1
        return res


""" Driver Code """
if __name__ == "__main__":
    """ 初始化队列 """
    queue = ArrayQueue(10)

    """ 元素入队 """
    queue.push(1)
    queue.push(3)
    queue.push(2)
    queue.push(5)
    queue.push(4)
    print("队列 queue =", queue.to_list())

    """ 访问队首元素 """
    peek = queue.peek()
    print("队首元素 peek =", peek)

    """ 元素出队 """
    poll = queue.poll()
    print("出队元素 poll =", poll)
    print("出队后 queue =", queue.to_list())

    """ 获取队列的长度 """
    size = queue.size()
    print("队列长度 size =", size)

    """ 判断队列是否为空 """
    is_empty = queue.is_empty()
    print("队列是否为空 =", is_empty)

    """ 测试环形数组 """
    for i in range(10):
        queue.push(i);
        queue.poll();
        print("第", i, "轮入队 + 出队后 queue = ", queue.to_list());