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0 likes • Jan 25, 2023
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class TreeNode {constructor(key, value = key, parent = null) {this.key = key;this.value = value;this.parent = parent;this.children = [];}get isLeaf() {return this.children.length === 0;}get hasChildren() {return !this.isLeaf;}}class Tree {constructor(key, value = key) {this.root = new TreeNode(key, value);}*preOrderTraversal(node = this.root) {yield node;if (node.children.length) {for (let child of node.children) {yield* this.preOrderTraversal(child);}}}*postOrderTraversal(node = this.root) {if (node.children.length) {for (let child of node.children) {yield* this.postOrderTraversal(child);}}yield node;}insert(parentNodeKey, key, value = key) {for (let node of this.preOrderTraversal()) {if (node.key === parentNodeKey) {node.children.push(new TreeNode(key, value, node));return true;}}return false;}remove(key) {for (let node of this.preOrderTraversal()) {const filtered = node.children.filter(c => c.key !== key);if (filtered.length !== node.children.length) {node.children = filtered;return true;}}return false;}find(key) {for (let node of this.preOrderTraversal()) {if (node.key === key) return node;}return undefined;}}const tree = new Tree(1, 'AB');tree.insert(1, 11, 'AC');tree.insert(1, 12, 'BC');tree.insert(12, 121, 'BG');[...tree.preOrderTraversal()].map(x => x.value);// ['AB', 'AC', 'BC', 'BCG']tree.root.value; // 'AB'tree.root.hasChildren; // truetree.find(12).isLeaf; // falsetree.find(121).isLeaf; // truetree.find(121).parent.value; // 'BC'tree.remove(12);[...tree.postOrderTraversal()].map(x => x.value);// ['AC', 'AB']
const express = require('express')const app = express()const port = 3000app.get('/', (req, res) => {res.send('Hello World!')})app.listen(port, () => {console.log(`Example app listening on port ${port}`)})
const flat = arr => [].concat.apply([], arr.map(a => Array.isArray(a) ? flat(a) : a));// Orconst flat = arr => arr.reduce((a, b) => Array.isArray(b) ? [...a, ...flat(b)] : [...a, b], []);// Or// See the browser compatibility at https://caniuse.com/#feat=array-flatconst flat = arr => arr.flat();// Exampleflat(['cat', ['lion', 'tiger']]); // ['cat', 'lion', 'tiger']
const toFixed = (n, fixed) => ~~(Math.pow(10, fixed) * n) / Math.pow(10, fixed);// ExamplestoFixed(25.198726354, 1); // 25.1toFixed(25.198726354, 2); // 25.19toFixed(25.198726354, 3); // 25.198toFixed(25.198726354, 4); // 25.1987toFixed(25.198726354, 5); // 25.19872toFixed(25.198726354, 6); // 25.198726
const longestPalindrome = (s) => {if(s.length === 1) return sconst odd = longestOddPalindrome(s)const even = longestEvenPalindrome(s)if(odd.length >= even.length) return oddif(even.length > odd.length) return even};const longestOddPalindrome = (s) => {let longest = 0let longestSubStr = ""for(let i = 1; i < s.length; i++) {let currentLongest = 1let currentLongestSubStr = ""let left = i - 1let right = i + 1while(left >= 0 && right < s.length) {const leftLetter = s[left]const rightLetter = s[right]left--right++if(leftLetter === rightLetter) {currentLongest += 2currentLongestSubStr = s.slice(left+1, right)} else break}if(currentLongest > longest) {if(currentLongestSubStr) longestSubStr = currentLongestSubStrelse longestSubStr = s[i]longest = currentLongest}}return longestSubStr}const longestEvenPalindrome = (s) => {let longest = 0let longestSubStr = ""for(let i = 0; i < s.length - 1; i++) {if(s[i] !== s[i+1]) continue;let currentLongest = 2let currentLongestSubStr = ""let left = i - 1let right = i + 2while(left >= 0 && right < s.length) {const leftLetter = s[left]const rightLetter = s[right]left--right++if(leftLetter === rightLetter) {currentLongest += 2currentLongestSubStr = s.slice(left+1, right)} else break}if(currentLongest > longest) {if(currentLongestSubStr) longestSubStr = currentLongestSubStrelse longestSubStr = s[i] + s[i+1]longest = currentLongest}}return longestSubStr}console.log(longestPalindrome("babad"))
const jwt = require("jsonwebtoken");const authToken = (req, res, next) => {const token = req.headers["x-auth-token"];try {req.user = jwt.verify(token, process.env.ACCESS_TOKEN_SECRET);next();} catch (err) {console.log(err.message);res.status(401).json({ msg: "Error authenticating token" });}};module.exports = authToken;