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| class Node():
"""节点"""
def __init__(self, item=None, next=None):
self.item = item
self.next = next
class Stack():
"""栈"""
def __init__(self, node=None):
self.head = node
def push(self, item):
"""栈顶插入元素"""
self.head = None(item, self.head)
def pop(self):
"""弹出栈顶元素"""
if self.head:
self.head=self.head.next
return
return "栈为空栈"
def peek(self):
"""返回栈顶元素"""
if self.head:
return self.head.item
return "栈为空栈"
def is_empty(self):
"""判断是否为空栈"""
return self.head==None
def size(self):
"""返回元素个数"""
num = 0
node = self.head
if node==None:
return num
num += 1
while node.next!=None:
node = node.next
num += 1
return num
|
