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Commit 2e49b5b

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feat: update 4 leetcode about queue and stack
1 parent 66932d6 commit 2e49b5b

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2 files changed

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/*
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* @lc app=leetcode id=225 lang=typescript
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*
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* [225] Implement Stack using Queues
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*/
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// @lc code=start
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// class ArrayQueue<number> {
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// private length: number; // 队列长度
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// private queue: number[]; // 队列
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// private head: number; // 队首指针
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// private tail: number; // 队尾指针
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// constructor(n: number) {
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// this.length = n;
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// this.queue = [];
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// this.head = 0;
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// this.tail = 0;
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// }
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// /**
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// * 入队
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// * 返回是否入队成功
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// * @param item
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// * @returns
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// */
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// enqueue(item: number): boolean {
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// if (this.tail === this.length) {
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// return false;
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// }
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// this.queue[this.tail] = item;
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// this.tail++;
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// return true;
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// }
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// /**
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// * 出队操作
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// * 返回队首值的同时,将指针往后移
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// * @returns
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// */
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// dequeue(): number | undefined | null {
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// if (this.head === this.tail) {
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// return null;
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// }
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// const item = this.queue[this.head];
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// this.head++;
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// return item;
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// }
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// }
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/**
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* @description: 两个队列实现栈
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* @param {number}
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* @return {MyStack}
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*/
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class MyStack {
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private outQueue: number[]; // 用于保存栈的弹出顺序
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private inQueue: number[];
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constructor() {
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this.outQueue = [];
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this.inQueue = [];
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}
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/**
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* @description: 通过两次转换使得队列顺序变成栈的顺序
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* [3, 1], [] => [3, 1], [5] => [], [5, 3, 1] => [5, 3, 1], []
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* @return {void}
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*/
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in2out(): void {
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while (this.outQueue.length) {
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this.inQueue.push(this.outQueue.shift());
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}
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while (this.inQueue.length) {
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this.outQueue.push(this.inQueue.shift());
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}
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}
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/**
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* @description: 往栈中推入数据
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* @param {number} x
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* @return {void}
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*/
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push(x: number): void {
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this.inQueue.push(x);
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this.in2out();
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}
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/**
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* @description: 栈中弹出数据
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* @return {number}
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*/
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pop(): number {
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return this.outQueue.shift();
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}
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/**
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* @description: 取栈尾的数据
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* @return {number}
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*/
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top(): number {
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return this.outQueue[0];
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}
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/**
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* @description: 栈是否为空
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* @return {boolean}
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*/
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empty(): boolean {
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return !this.outQueue.length;
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}
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}
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/**
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* Your MyStack object will be instantiated and called as such:
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* var obj = new MyStack()
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* obj.push(x)
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* var param_2 = obj.pop()
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* var param_3 = obj.top()
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* var param_4 = obj.empty()
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*/
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// @lc code=end
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/*
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* @lc app=leetcode id=232 lang=typescript
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*
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* [232] Implement Queue using Stacks
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*/
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// @lc code=start
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/**
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* @description: 双栈思想
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*/
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class MyQueue {
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private inStack: number[];
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private outStack: number[];
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constructor() {
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this.inStack = [];
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this.outStack = [];
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}
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/**
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* @description: 从第一个栈里弹出数据到第二个栈,此时第二个栈再弹出就是队列的顺序
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* @return {void}
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*/
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private in2out(): void {
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while (this.inStack.length) {
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this.outStack.push(this.inStack.pop());
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}
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}
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/**
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* @description: 往队末推入元素
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* @param {number} x
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* @return {void}
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*/
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public push(x: number): void {
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this.inStack.push(x);
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}
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/**
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* @description: 弹出队首元素
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* @return {number}
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*/
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public pop(): number {
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if (!this.outStack.length) {
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this.in2out();
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}
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return this.outStack.pop();
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}
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/**
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* @description: 取队首元素
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* @return {number}
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*/
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public peek(): number {
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if (!this.outStack.length) {
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this.in2out();
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}
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return this.outStack[this.outStack.length - 1];
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}
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/**
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* @description: 队列是否为空
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* @return {boolean}
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*/
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public empty(): boolean {
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return this.inStack.length === 0 && this.outStack.length === 0;
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}
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}
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/**
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* Your MyQueue object will be instantiated and called as such:
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* var obj = new MyQueue()
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* obj.push(x)
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* var param_2 = obj.pop()
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* var param_3 = obj.peek()
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* var param_4 = obj.empty()
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*/
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// @lc code=end

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