题目描述
定义栈的数据结构,请在该类型中实现一个能够得到栈中所含最小元素的min函数(时间复杂度应为O(1))。
class Solution:
def __init__(self):
self.stack = []
self.minstack = []
def push(self, node):
if not self.minstack:
self.minstack.append(node)
else:
self.minstack.append(min(self.minstack[-1],node))
self.stack.append(node)
def pop(self):
if not self.stack:
return None
self.minstack.pop()
return self.stack.pop()
def top(self):
if not self.stack:
return None
return self.stack[-1]
def min(self):
if not self.stack:
return None
return self.minstack[-1]