python 通过双栈实现队列

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开始做法

# coding:utf-8# !/usr/bin/env python# Time: 2018/6/6 9:32# Author: sty# File: stack_queue.pyclass Solution():def __init__(self):self.stack1 = []self.stack2 = []def push(self, data):self.stack1.append(data)def pop(self):if len(self.stack1) == 0 and len(self.stack2) == 0:return []elif len(self.stack2) == 0:while len(self.stack1) != 0:self.stack2.append(self.stack1.pop())return self.stack2.pop()

优化做法

减少了一次stack2的入栈和出栈操作

class Solution():def __init__(self):self.stack1 = []self.stack2 = []def push(self, data):self.stack1.append(data)def pop(self):if len(self.stack1) == 0 and len(self.stack2) == 0:return []elif len(self.stack2) == 0:while len(self.stack1) != 1:self.stack2.append(self.stack1.pop())# 减少了一次stack2的入栈和出栈操作return self.stack1.pop()return self.stack2.pop()

全部操作合集

class MyQueue:def __init__(self):"""Initialize your data structure here."""self.stack1 = []self.stack2 = []def push(self, x):"""Push element x to the back of queue.:type x: int:rtype: void"""self.stack1.append(x)def pop(self):"""Removes the element from in front of queue and returns that element.:rtype: int"""if len(self.stack1) == 0 and len(self.stack2) == 0:return Noneelse:if len(self.stack2) == 0:while len(self.stack1) != 1:self.stack2.append(self.stack1.pop())return self.stack1.pop()else:return self.stack2.pop()def peek(self):"""Get the front element.:rtype: int"""if len(self.stack2) == 0 and len(self.stack1) == 0:return Noneelse:if len(self.stack2) == 0:return self.stack1[0]else:return self.stack2[-1]def empty(self):"""Returns whether the queue is empty.:rtype: bool"""if len(self.stack1) == 0 and len(self.stack2) == 0:return Trueelse:return False

参考文档

https://www.cnblogs.com/wanghui9072229/archive/2011/11/22/2259391.html
https://blog.csdn.net/slibra_L/article/details/78098683
https://leetcode.com/problems/implement-queue-using-stacks/description/

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