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

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


class ArrayQueue:
    """基於環形陣列實現的佇列"""

    def __init__(self, size: int):
        """建構子"""
        self._nums: list[int] = [0] * size  # 用於儲存佇列元素的陣列
        self._front: int = 0  # 佇列首指標，指向佇列首元素
        self._size: int = 0  # 佇列長度

    def capacity(self) -> int:
        """獲取佇列的容量"""
        return len(self._nums)

    def size(self) -> int:
        """獲取佇列的長度"""
        return self._size

    def is_empty(self) -> bool:
        """判斷佇列是否為空"""
        return self._size == 0

    def push(self, num: int):
        """入列"""
        if self._size == self.capacity():
            raise IndexError("佇列已滿")
        # 計算佇列尾指標，指向佇列尾索引 + 1
        # 透過取餘操作實現 rear 越過陣列尾部後回到頭部
        rear: int = (self._front + self._size) % self.capacity()
        # 將 num 新增至佇列尾
        self._nums[rear] = num
        self._size += 1

    def pop(self) -> int:
        """出列"""
        num: int = self.peek()
        # 佇列首指標向後移動一位，若越過尾部，則返回到陣列頭部
        self._front = (self._front + 1) % self.capacity()
        self._size -= 1
        return num

    def peek(self) -> int:
        """訪問佇列首元素"""
        if self.is_empty():
            raise IndexError("佇列為空")
        return self._nums[self._front]

    def to_list(self) -> list[int]:
        """返回串列用於列印"""
        res = [0] * self.size()
        j: int = self._front
        for i in range(self.size()):
            res[i] = self._nums[(j % self.capacity())]
            j += 1
        return res


"""Driver Code"""
if __name__ == "__main__":
    # 初始化佇列
    queue = ArrayQueue(10)

    # 元素入列
    queue.push(1)
    queue.push(3)
    queue.push(2)
    queue.push(5)
    queue.push(4)
    print("佇列 queue =", queue.to_list())

    # 訪問佇列首元素
    peek: int = queue.peek()
    print("佇列首元素 peek =", peek)

    # 元素出列
    pop: int = queue.pop()
    print("出列元素 pop =", pop)
    print("出列後 queue =", queue.to_list())

    # 獲取佇列的長度
    size: int = queue.size()
    print("佇列長度 size =", size)

    # 判斷佇列是否為空
    is_empty: bool = queue.is_empty()
    print("佇列是否為空 =", is_empty)

    # 測試環形陣列
    for i in range(10):
        queue.push(i)
        queue.pop()
        print("第", i, "輪入列 + 出列後 queue = ", queue.to_list())