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const nums = [1, 2, 3];const strs = Array.from('est');nums.push(6);nums.push(4, 9);strs.unshift('t');nums.length; // 6nums[nums.length - 1]; // 9strs[0]; // 't'strs[2]; // 's'nums.slice(1, 3); // [2, 3]nums.map(n => n * 2); // [2, 4, 6, 12, 8, 18]nums.filter(n => n % 2 === 0); // [2, 6, 4]nums.reduce((a, n) => a + n, 0); // 25strs.reverse(); // ['t', 's', 'e', 't']strs.join(''); // 'test'const nums = new Set([1, 2, 3]);nums.add(4);nums.add(1);nums.add(5);nums.add(4);nums.size; // 5nums.has(4); // truenums.delete(4);nums.has(4); // false[...nums]; // [1, 2, 3, 5]nums.clear();nums.size; // 0const items = new Map([[1, { name: 'John' }],[2, { name: 'Mary' }]]);items.set(4, { name: 'Alan' });items.set(2, { name: 'Jeff' });items.size; // 3items.has(4); // trueitems.get(2); // { name: 'Jeff' }items.delete(2);items.size; // 2[...items.keys()]; // [1, 4][...items.values()]; // [{ name: 'John' }, { name: 'Alan' }]items.clear();items.size; // 0
// Time Complexity : O(N)// Space Complexity : O(1)var isMonotonic = function(nums) {let isMono = null;for(let i = 1; i < nums.length; i++) {if(isMono === null) {if(nums[i - 1] < nums[i]) isMono = 0;else if(nums[i - 1] > nums[i]) isMono = 1;continue;}if(nums[i - 1] < nums[i] && isMono !== 0) {return false;}else if(nums[i - 1] > nums[i] && isMono !== 1) {return false;}}return true;};let nums1 = [1,2,2,3]let nums2 = [6,5,4,4]let nums3 = [1,3,2]console.log(isMonotonic(nums1));console.log(isMonotonic(nums2));console.log(isMonotonic(nums3));
class LinkedList {constructor() {this.nodes = [];}get size() {return this.nodes.length;}get head() {return this.size ? this.nodes[0] : null;}get tail() {return this.size ? this.nodes[this.size - 1] : null;}insertAt(index, value) {const previousNode = this.nodes[index - 1] || null;const nextNode = this.nodes[index] || null;const node = { value, next: nextNode };if (previousNode) previousNode.next = node;this.nodes.splice(index, 0, node);}insertFirst(value) {this.insertAt(0, value);}insertLast(value) {this.insertAt(this.size, value);}getAt(index) {return this.nodes[index];}removeAt(index) {const previousNode = this.nodes[index - 1];const nextNode = this.nodes[index + 1] || null;if (previousNode) previousNode.next = nextNode;return this.nodes.splice(index, 1);}clear() {this.nodes = [];}reverse() {this.nodes = this.nodes.reduce((acc, { value }) => [{ value, next: acc[0] || null }, ...acc],[]);}*[Symbol.iterator]() {yield* this.nodes;}}const list = new LinkedList();list.insertFirst(1);list.insertFirst(2);list.insertFirst(3);list.insertLast(4);list.insertAt(3, 5);list.size; // 5list.head.value; // 3list.head.next.value; // 2list.tail.value; // 4[...list.map(e => e.value)]; // [3, 2, 1, 5, 4]list.removeAt(1); // 2list.getAt(1).value; // 1list.head.next.value; // 1[...list.map(e => e.value)]; // [3, 1, 5, 4]list.reverse();[...list.map(e => e.value)]; // [4, 5, 1, 3]list.clear();list.size; // 0
function printHeap(heap, index, level) {if (index >= heap.length) {return;}console.log(" ".repeat(level) + heap[index]);printHeap(heap, 2 * index + 1, level + 1);printHeap(heap, 2 * index + 2, level + 1);}//You can call this function by passing in the heap array and the index of the root node, which is typically 0, and level = 0.let heap = [3, 8, 7, 15, 17, 30, 35, 2, 4, 5, 9];printHeap(heap,0,0)
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;
const copyToClipboard = str => {const el = document.createElement('textarea');el.value = str;el.setAttribute('readonly', '');el.style.position = 'absolute';el.style.left = '-9999px';document.body.appendChild(el);const selected =document.getSelection().rangeCount > 0? document.getSelection().getRangeAt(0): false;el.select();document.execCommand('copy');document.body.removeChild(el);if (selected) {document.getSelection().removeAllRanges();document.getSelection().addRange(selected);}};copyToClipboard('Lorem ipsum'); // 'Lorem ipsum' copied to clipboard.