软件测试/测试开发丨Python 数据结构与算法

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本文为霍格沃兹测试开发学社学员学习笔记分享
原文链接：https://ceshiren.com/t/topic/26451

堆栈

数组和列表暴露了太多的接口，虽然操作灵活，但不可控，容易出错。如果在插入位置写错数据将会改变整个数组的内容
栈是**操作受限的列表

栈只能在一端进行删除和插入操作，遵循先进后出后进先出的原则

• 数组栈

class ArrayStack:
    def __init__(self, volume):
        self.vol = volume
        self.count = 0
        self.data = [-1] * volume

    def in_stack(self, value):
        """入栈"""
        if self.count == self.vol:
            return False
        self.data[self.count] = value
        self.count += 1
        return True

    def de_stack(self):
        """出栈"""
        if self.count == 0:
            return None
        self.count -= 1
        return self.data[self.count]


def test_stack():
    array_stack = ArrayStack(5)
    data = ["a", "b", "c", "d", "e"]
    for i in data:
        array_stack.in_stack(i)
    result = array_stack.in_stack("a")
    assert not result
    data.reverse()
    for i in data:
        assert i == array_stack.de_stack()
    assert not array_stack.de_stack()

入栈时间复杂度：O(1)
出栈时间复杂度：O(1)

• 链式栈

class LinkStack:
    class Node:
        def __init__(self, data):
            self.data = data
            self.next = None

    def __init__(self):
        self.top = None

    def en_stack(self, value):
        """入栈"""
        new_node = self.Node(value)
        if self.top is None:
            self.top = new_node
        else:
            new_node.next = self.top
            self.top = new_node

    def de_stack(self):
        """出栈"""
        if self.top is None:
            return -1
        result = self.top.data
        self.top = self.top.next
        return result


def test_link_stack():
    link_stack = LinkStack()
    data = [1, 2, 3, 4, 5]
    for i in data:
        link_stack.en_stack(i)
    data.reverse()
    for j in data:
        assert j == link_stack.de_stack()
    assert link_stack.de_stack() == -1

入栈时间复杂度：O(1)
出栈时间复杂度：O(1)