数据结构链表之栈
栈的概述
- 定义：栈是一种基于先进后出(FILO)的数据结构，是一种只能在一段进行插入和删除操作的特殊线性表。
- 引入名词：将数据存入栈的动作称为压栈，将数据取出栈的动作称为弹栈
- 栈的特点：先进入栈的元素会被压入栈底，最后一位元素所处的位置就是栈顶，弹栈时最后一个元素最先被读取，依次往下取出，因此叫做First In Last Out
栈可以用顺序表(python中列表)实现，也可以用链表实现，这里实现的方式的是使用链表，有兴趣的同学可以自己编写代码用列表实现栈
python代码实现：
class Node:def __init__(self, item):self.item = itemself.next = Noneclass Stack:def __init__(self):self.head = Noneself.len = 0def is_empty(self):return not self.len# def length(self):# return self.lendef push(self, item):"""Push an element into the stack"""node = Node(item)node.next = self.headself.head = nodeself.len += 1def pop(self):"""Pop a value from the stack top"""# if not self.head:# raise IndexError("pop from empty list")cur = self.headif self.head:self.head = self.head.nextself.len -= 1return cur# Make the Stack iterabledef __iter__(self):self.cur = self.head# if not self.cur:# raise StopIteration # The error here will be raised if the condition were reachedreturn selfdef __next__(self):if not self.cur:raise StopIteration # The error here actually won't be raisedtry:temp = self.curself.cur = self.cur.nextreturn tempexcept AttributeError as e:raise StopIteration
主要实现的功能：
- is_empty()判断栈是否为空
- length()同len属性，可以返回栈的长度
- push()向栈压入元素
- pop()从栈顶取出一个元素
- 重写的__iter__()和__next__()用于实现栈的遍历功能
功能验证
if __name__ == "__main__":stack = Stack()print(f"Is empty? {stack.is_empty()}")print("Push elements into the stack:")stack.push('a')stack.push('b')stack.push('c')stack.push('d')# Iterate the stackfor item in stack:print(item.item, end=' ')print(f"\nPop a value from the top stack: {stack.pop().item}")print(f"The number(length) of the remanent nodes is: {stack.len}")
输出结果：
Is empty? True
Push elements into the stack:
d c b a
Pop a value from the top stack: d
The number(length) of the remanent nodes is: 3
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