Title Description
Stack data structure definition, implement this type can be a min function smallest elements contained in the stack (should the time complexity O (1)).
ps: the test when the stack is not empty when, on the call stack pop () or min () or top () method.
Thinking
Dual-stack, is a common memory, the other is used to store a minimum value.
# -*- coding:utf-8 -*-
class Solution:
def __init__(self):
self.stack = []
self.ministack = []
def push(self, node):
if len(self.ministack)>0:
if node <= self.ministack[-1]:
self.ministack.append(node)
self.stack.append(node)
else:
self.ministack.append(node)
self.stack.append(node)
def pop(self):
node = self.stack.pop()
if node == self.ministack[-1]:
self.ministack.pop()
return node
def top(self):
return self.stack[-1]
def min(self):
return self.ministack[-1]
Stack had hit a big nod, afraid of careless use of the index
