[雪峰磁针石博客]Python经典面试题: 用3种方法实现堆栈和队列并示例实际应用场景

介绍

数据结构在计算机中组织存储，以便我们可以有效地访问和更改数据。 堆栈和队列是计算机科学中定义的最早的数据结构。

堆栈

遵循后进先出 (Last-in-First-Out LIFO)原则。

• push - 在堆栈顶部添加元素：

• pop - 删除堆栈顶部的元素：

队列

遵循先入先出(FIFO:First-in-First-Out)原则。

• enqueue - 在队列的开头添加元素：

• dequeue - 删除队列开头的元素：

使用列表实现堆栈和队列

Python的内置List数据结构k堆栈和队列操作的方法。

堆栈

letters = [] # Let's push some letters into our list letters.append('c') letters.append('a') letters.append('t') letters.append('g') # Now let's pop letters, we should get 'g' last_item = letters.pop() print(last_item) # If we pop again we'll get 't' last_item = letters.pop() print(last_item) # 'c' and 'a' remain print(letters) # ['c', 'a'] 

执行结果

g t ['c', 'a']

队列

fruits = [] # Let's enqueue some fruits into our list fruits.append('banana') fruits.append('grapes') fruits.append('mango') fruits.append('orange') # Now let's dequeue our fruits, we should get 'banana' first_item = fruits.pop(0) print(first_item) # If we dequeue again we'll get 'grapes' first_item = fruits.pop(0) print(first_item) # 'mango' and 'orange' remain print(fruits) # ['c', 'a'] 

执行结果

banana grapes ['mango', 'orange']

使用Deque库的堆栈和队列

deque是Double Ended Queue的缩写 - 可以获取存储的第一个或最后一个元素的通用队列，下面我们使用Deque库的堆栈和队列：

from collections import deque # you can initialize a deque with a list numbers = deque() # Use append like before to add elements numbers.append(99) numbers.append(15) numbers.append(82) numbers.append(50) numbers.append(47) # You can pop like a stack last_item = numbers.pop() print(last_item) # 47 print(numbers) # deque([99, 15, 82, 50]) # You can dequeue like a queue first_item = numbers.popleft() print(first_item) # 99 print(numbers) # deque([15, 82, 50]) 

执行结果

47 deque([99, 15, 82, 50]) 99 deque([15, 82, 50])

参考资料

• 本文最新版本地址
• 本文涉及的python测试开发库 谢谢点赞！
• 本文相关海量书籍下载
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• python GUI工具书籍下载-持续更新

更严格的实现

创建撤消功能 - 允许用户回溯他们的操作，直到会话开始。堆栈是这种情况的理想选择。 我们可以通过将其推送到堆栈来记录用户所采取的每个操作。 当用户想要撤消操作时，他们将从堆栈中弹出它。

游戏中，每次按下按钮，都会触发输入事件。 测试人员注意到，如果按钮按下得太快，游戏只处理第一个按钮，特殊动作将无效！可以使用队列修复它。 我们可以将所有输入事件排入队列。

#!/usr/bin/python3 # -*- coding: utf-8 -*- # 项目实战讨论QQ群630011153 144081101 # python测试开发库汇总: https://github.com/china-testing/python-api-tesing/ # 本文最佳板式地址： https://www.jianshu.com/p/c990427ca608 # A simple class stack that only allows pop and push operations class Stack: def __init__(self): self.stack = [] def pop(self): if len(self.stack) < 1: return None return self.stack.pop() def push(self, item): self.stack.append(item) def size(self): return len(self.stack) # And a queue that only has enqueue and dequeue operations class Queue: def __init__(self): self.queue = [] def enqueue(self, item): self.queue.append(item) def dequeue(self): if len(self.queue) < 1: return None return self.queue.pop(0) def size(self): return len(self.queue) document_actions = Stack() # The first enters the title of the document document_actions.push('action: enter; text_id: 1; text: This is my favourite document') # Next they center the text document_actions.push('action: format; text_id: 1; alignment: center') # As with most writers, the user is unhappy with the first draft and undoes the center alignment document_actions.pop() # The title is better on the left with bold font document_actions.push('action: format; text_id: 1; style: bold') input_queue = Queue() # The player wants to get the upper hand so pressing the right combination of buttons quickly input_queue.enqueue('DOWN') input_queue.enqueue('RIGHT') input_queue.enqueue('B') # Now we can process each item in the queue by dequeueing them key_pressed = input_queue.dequeue() # 'DOWN' # We'll probably change our player position key_pressed = input_queue.dequeue() # 'RIGHT' # We'll change the player's position again and keep track of a potential special move to perform key_pressed = input_queue.dequeue() # 'B' # This can do the act, but the game's logic will know to do the special move