数据结构与算法-栈

一、栈的特点

保证元素后进先出关系的容器

二、顺序栈

栈的空间是固定的，顺序对里面的元素进行入栈，出栈

class Stack:
    def __init__(self, maxsize):
        self.max = maxsize  # 栈的最大容量
        self.elem = [None for i in self.max]  # 顺序栈
        self.top = 0  # 栈顶指针
        self.base = 0  # 栈底指针

    # 压栈
    def push(self, elem):
        if self.top - self.base == self.max:
            print("栈已满")
            return False
        self.elem[self.top] = elem
        self.top += 1

    # 弹栈
    def pop(self):
        if self.top == 0:
            print("栈为空")
            return False
        self.elem[self.top] = None
        self.top -= 1

    # 取栈顶元素
    def get_top(self):
        return self.elem[self.top - 1]

三、链栈

可以动态实现栈空间的增减

# 链栈节点类
class StackNode:
    def __init__(self, elem=None):
        self.elem = elem  # 数据
        self.next = None  # 指针

# 链栈类
class LinkStack:
    def __init__(self):
        self.link_top = None  # 链栈的指针，指向栈顶元素

    # 压栈
    def push(self, elem):
        s = StackNode(elem)
        s.next = self.link_top
        self.link_top = s

    # 弹栈
    def pop(self):
        node = self.link_top.elem
        self.link_top = self.link_top.next
        return node
    
    # 获取栈顶元素
    def get_top_elem(self):
        return self.link_top.elem
    
    # 获取链栈长度
    def get_len(self):
        top = self.link_top
        count = 0
        while top:
            count += 1
            top = top.next
        return count