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Commit 5aaac07

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feat: update 4 leetcode about stack and linkedlist
1 parent c578819 commit 5aaac07

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5 files changed

+246
-1
lines changed

5 files changed

+246
-1
lines changed

‎.vscode/settings.json

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{
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"editor.detectIndentation": false
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}

‎leetcode/146.lru-cache.ts

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/*
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* @lc app=leetcode id=146 lang=typescript
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*
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* [146] LRU Cache
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*/
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// @lc code=start
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interface cache {
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key: number;
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value: number;
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}
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/**
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* LRU 缓存淘汰算法-数组实现
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*/
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class LRUCache {
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private cacheList: cache[]; // 缓存数组
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private maxCacheLength: number; // 缓存容量
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constructor(capacity: number) {
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this.cacheList = [];
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this.maxCacheLength = capacity;
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}
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/**
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* 缓存的读取
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* @param key
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* @returns
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*/
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get(key: number): number {
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// 查找索引是否存在
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const cachedIndex = this.cacheList.findIndex((item: cache): boolean => item.key === key);
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if (cachedIndex === -1) {
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return cachedIndex;
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}
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// 修改原缓存数组
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const [cached] = this.cacheList.splice(cachedIndex, 1);
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// 把最近读取的放在第一位
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this.cacheList.unshift(cached);
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return cached.value;
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}
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/**
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* 缓存的修改
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* @param key
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* @param value
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* @returns
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*/
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put(key: number, value: number): void {
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// 首先查找是否原先已缓存
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const cachedIndex = this.cacheList.findIndex((item: cache): boolean => item.key === key);
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// 如果已缓存,就更新值
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if (cachedIndex !== -1) {
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// 删除原先的缓存内容
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this.cacheList.splice(cachedIndex, 1);
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// 进行更新,放到最近的位置
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this.cacheList.unshift({ key, value });
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return;
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} else {
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this.cacheList.unshift({ key, value });
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// 如果超出了,就移除最早缓存的
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this.cacheList.length > this.maxCacheLength && this.cacheList.pop();
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return;
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}
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}
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}
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/**
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* Your LRUCache object will be instantiated and called as such:
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* var obj = new LRUCache(capacity)
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* var param_1 = obj.get(key)
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* obj.put(key,value)
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*/
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// @lc code=end

‎leetcode/155.min-stack.ts

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/*
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* @lc app=leetcode id=155 lang=typescript
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*
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* [155] Min Stack
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*/
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// @lc code=start
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/**
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* 用纯数组的方式解决
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* 时间复杂度 O(1)
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* 空间复杂度 O(n)
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*/
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class MinStack {
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private stack: number[]; // 数据栈
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private minStack: number[]; // 辅助栈:用于保存最小栈,需要把每个值都保存,最小值在栈顶
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public constructor() {
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this.stack = [];
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this.minStack = [Number.MAX_SAFE_INTEGER];
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}
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/**
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* 栈的推入
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* @param value
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* @returns
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*/
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public push(value: number): void {
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this.stack.push(value);
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// 注意这里推入的并不一定是传入的值,如果这个值比当前值大,那么推入会是原先的较小值
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// 这么做的目的是为了保存辅助栈和数据栈的同步
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this.minStack.push(Math.min(this.minStack[this.minStack.length - 1], value));
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}
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/**
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* 栈的弹出(在非空栈上调用)
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* @returns
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*/
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public pop(): void {
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this.stack.pop();
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this.minStack.pop();
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}
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/**
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* 获取栈顶元素
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* @returns
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*/
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public top(): number {
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return this.stack[this.stack.length - 1];
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}
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/**
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* 获取栈中的最小值
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* 时间复杂度 O(1)
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* @returns
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*/
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getMin(): number {
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return this.minStack[this.minStack.length - 1];
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}
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}
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class MinStack2 {
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private items: number[];
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private count: number;
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public constructor() {
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this.items = [];
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this.count = 0;
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}
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/**
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* 栈的推入
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* @param value
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* @returns
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*/
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public push(value: number): void {
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// if (this.count === this.length) {
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// return;
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// }
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this.items[this.count++] = value;
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// this.items.push(value);
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}
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/**
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* 栈的弹出(在非空栈上调用)
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* @returns
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*/
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public pop(): void {
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// if (this.count === 0) {
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// return null;
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// }
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this.count--;
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const value: number = this.items[this.count]; // 不用数组 API 的方式,需要将 count 先减去多的
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this.items.length = this.count; // 注意一定要清除
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// return this.items.pop();
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}
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/**
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* 获取栈顶元素
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* @returns
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*/
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public top(): number {
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// 题目中不存在非空栈
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// if (this.count === 0) {
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// return null;
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// }
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const value: any = this.items[this.count - 1]; // 不用数组 API 的方式,需要将 count 先减去多的
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return value;
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}
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/**
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* 获取栈中的最小值
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* 时间复杂度 O(n)
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* @returns
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*/
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getMin(): number {
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let minValue = Number.MAX_SAFE_INTEGER;
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this.items.forEach((value) => {
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if (value < minValue) {
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minValue = value;
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}
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});
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return minValue;
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}
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}
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/**
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* Your MinStack object will be instantiated and called as such:
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* var obj = new MinStack()
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* obj.push(val)
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* obj.pop()
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* var param_3 = obj.top()
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* var param_4 = obj.getMin()
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*/
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// @lc code=end
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/*
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* @lc app=leetcode id=876 lang=typescript
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*
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* [876] Middle of the Linked List
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*/
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// @lc code=start
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/**
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* Definition for singly-linked list.
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* class ListNode {
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* val: number
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* next: ListNode | null
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* constructor(val?: number, next?: ListNode | null) {
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* this.val = (val===undefined ? 0 : val)
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* this.next = (next===undefined ? null : next)
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* }
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* }
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*/
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function middleNode(head: ListNode | null): ListNode | null {
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if (head === null || head.next === null) {
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return head;
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}
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let slow = head;
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let fast = head;
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while (fast && fast.next !== null) {
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slow = slow.next;
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fast = fast.next.next;
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}
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return slow;
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};
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// @lc code=end

‎leetcode/912.sort-an-array.js

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}
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// 如何选择基准值,用中间索引来获取
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let baseIndex = Math.floor(arr.length / 2);
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// 取出中间值
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// 取出中间值,注意也修改了原数组,使得数组去掉中间值进行的遍历
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let baseVal = arr.splice(baseIndex, 1)[0];
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let left = [];
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let right = [];

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