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const MongoClient = require('mongodb').MongoClient;const assert = require('assert');// Connection URLconst url = 'mongodb://localhost:27017';// Database Nameconst dbName = 'myproject';// Use connect method to connect to the serverMongoClient.connect(url, function(err, client) {assert.equal(null, err);console.log("Connected successfully to server");const db = client.db(dbName);client.close();});
var invertTree = function(root) {const reverseNode = node => {if (node == null) {return null}reverseNode(node.left);reverseNode(node.right);let holdLeft = node.left;node.left = node.right;node.right = holdLeft;return node;}return reverseNode(root);};
function sortNumbers(arr) {return arr.slice().sort((a, b) => a - b);}const unsortedArray = [4, 1, 9, 6, 3, 5];const sortedArray = sortNumbers(unsortedArray);console.log("Unsorted Numbers:", unsortedArray);console.log("\n");console.log("Sorted Numbers:", sortedArray);
class Graph {constructor(directed = true) {this.directed = directed;this.nodes = [];this.edges = new Map();}addNode(key, value = key) {this.nodes.push({ key, value });}addEdge(a, b, weight) {this.edges.set(JSON.stringify([a, b]), { a, b, weight });if (!this.directed)this.edges.set(JSON.stringify([b, a]), { a: b, b: a, weight });}removeNode(key) {this.nodes = this.nodes.filter(n => n.key !== key);[...this.edges.values()].forEach(({ a, b }) => {if (a === key || b === key) this.edges.delete(JSON.stringify([a, b]));});}removeEdge(a, b) {this.edges.delete(JSON.stringify([a, b]));if (!this.directed) this.edges.delete(JSON.stringify([b, a]));}findNode(key) {return this.nodes.find(x => x.key === key);}hasEdge(a, b) {return this.edges.has(JSON.stringify([a, b]));}setEdgeWeight(a, b, weight) {this.edges.set(JSON.stringify([a, b]), { a, b, weight });if (!this.directed)this.edges.set(JSON.stringify([b, a]), { a: b, b: a, weight });}getEdgeWeight(a, b) {return this.edges.get(JSON.stringify([a, b])).weight;}adjacent(key) {return [...this.edges.values()].reduce((acc, { a, b }) => {if (a === key) acc.push(b);return acc;}, []);}indegree(key) {return [...this.edges.values()].reduce((acc, { a, b }) => {if (b === key) acc++;return acc;}, 0);}outdegree(key) {return [...this.edges.values()].reduce((acc, { a, b }) => {if (a === key) acc++;return acc;}, 0);}}const g = new Graph();g.addNode('a');g.addNode('b');g.addNode('c');g.addNode('d');g.addEdge('a', 'c');g.addEdge('b', 'c');g.addEdge('c', 'b');g.addEdge('d', 'a');g.nodes.map(x => x.value); // ['a', 'b', 'c', 'd'][...g.edges.values()].map(({ a, b }) => `${a} => ${b}`);// ['a => c', 'b => c', 'c => b', 'd => a']g.adjacent('c'); // ['b']g.indegree('c'); // 2g.outdegree('c'); // 1g.hasEdge('d', 'a'); // trueg.hasEdge('a', 'd'); // falseg.removeEdge('c', 'b');[...g.edges.values()].map(({ a, b }) => `${a} => ${b}`);// ['a => c', 'b => c', 'd => a']g.removeNode('c');g.nodes.map(x => x.value); // ['a', 'b', 'd'][...g.edges.values()].map(({ a, b }) => `${a} => ${b}`);// ['d => a']g.setEdgeWeight('d', 'a', 5);g.getEdgeWeight('d', 'a'); // 5
arr = [] // empty arrayconst isEmpty = arr => !Array.isArray(arr) || arr.length === 0;// ExamplesisEmpty([]); // trueisEmpty([1, 2, 3]); // false
const kMeans = (data, k = 1) => {const centroids = data.slice(0, k);const distances = Array.from({ length: data.length }, () =>Array.from({ length: k }, () => 0));const classes = Array.from({ length: data.length }, () => -1);let itr = true;while (itr) {itr = false;for (let d in data) {for (let c = 0; c < k; c++) {distances[d][c] = Math.hypot(...Object.keys(data[0]).map(key => data[d][key] - centroids[c][key]));}const m = distances[d].indexOf(Math.min(...distances[d]));if (classes[d] !== m) itr = true;classes[d] = m;}for (let c = 0; c < k; c++) {centroids[c] = Array.from({ length: data[0].length }, () => 0);const size = data.reduce((acc, _, d) => {if (classes[d] === c) {acc++;for (let i in data[0]) centroids[c][i] += data[d][i];}return acc;}, 0);for (let i in data[0]) {centroids[c][i] = parseFloat(Number(centroids[c][i] / size).toFixed(2));}}}return classes;};kMeans([[0, 0], [0, 1], [1, 3], [2, 0]], 2); // [0, 1, 1, 0]