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chapter 07: sets
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‎src/07-set/01-using-myset-class.js‎

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// src/07-set/01-using-myset-class.js
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const MySet = require('./set');
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const article = {
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title: 'The importance of data structures in programming',
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content: '...',
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tags: new MySet() // using MySet to store tags
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};
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// add tags
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article.tags.add('programming');
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article.tags.add('data structures');
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article.tags.add('algorithms');
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article.tags.add('programming');
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console.log(article.tags.size); // 3
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console.log(article.tags.has('data structures')); // true
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console.log(article.tags.has('algorithms')); // true
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console.log(article.tags.has('programming')); // true
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console.log(article.tags.has('javascript')); // false
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console.log(article.tags.values()); // ['programming', 'data structures', 'algorithms']
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// remove tags
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article.tags.delete('programming');
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article.tags.add('JavaScript');
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console.log(article.tags.values()); // ['data structures', 'algorithms', 'JavaScript']
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// union example
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const interestsFromWebsites = new MySet();
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interestsFromWebsites.addAll(['technology', 'politics', 'photography']);
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const interestsFromSocialMedia = new MySet();
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interestsFromSocialMedia.addAll(['technology', 'movies', 'books']);
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const allInterests = interestsFromWebsites.union(interestsFromSocialMedia);
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console.log(allInterests.values()); // ['technology', 'politics', 'photography', 'movies', 'books']
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// intersection example
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const job1Skills = new MySet();
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job1Skills.addAll(['JavaScript', 'Angular', 'Java', 'SQL']);
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const job2Skills = new MySet();
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job2Skills.addAll(['Python', 'Machine Learning', 'SQL', 'Statistics']);
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const jobPostings =
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[{
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title: 'Software Engineer',
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skills: job1Skills
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},
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{
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title: 'Data Scientist',
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skills: job2Skills
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}];
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const candidateSkills = new MySet();
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candidateSkills.addAll(['JavaScript', 'Angular', 'TypeScript', 'AWS']);
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const candidate = {
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name: 'Loiane',
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skills: candidateSkills
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};
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// Function to match candidate with jobs
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function matchCandidateWithJobs(candidate, jobPostings) {
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const matches = [];
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for (const job of jobPostings) {
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const matchingSkillsSet = candidate.skills.intersection(job.skills);
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if (!matchingSkillsSet.isEmpty()){
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matches.push({
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title: job.title,
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matchingSkills: matchingSkillsSet.values()
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});
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}
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}
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return matches;
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}
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// Find matching jobs for the candidate
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const matchingJobs = matchCandidateWithJobs(candidate, jobPostings);
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console.log(matchingJobs);
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// output: [{ title: 'Software Engineer', matchingSkills: [ 'JavaScript', 'Angular' ] }]
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// difference example
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// Sets representing subscriber interests
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const allSubscribers = new MySet();
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allSubscribers.addAll(['Aelin', 'Rowan', 'Xaden', 'Poppy', 'Violet']);
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const booksInterested = new MySet();
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booksInterested.addAll(['Aelin', 'Poppy', 'Violet']);
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const alreadyPurchasedBooks = new MySet();
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alreadyPurchasedBooks.addAll(['Poppy']);
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// Find subscribers interested in books but haven't purchased yet
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const targetSubscribers = booksInterested.difference(alreadyPurchasedBooks);
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// Send targeted email
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targetSubscribers.values().forEach(subscriber => {
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sendEmail(subscriber, 'New books you will love!');
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});
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function sendEmail(subscriber, message) {
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console.log(`Sending email to ${subscriber}: ${message}`);
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}
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// Sending email to Aelin: New books you will love!
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// Sending email to Violet: New books you will love!
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// subset example
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// Example Recipe Data
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const chickenIngredients = new MySet()
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chickenIngredients.addAll(['chicken', 'tomato', 'onion', 'garlic', 'ginger', 'spices']);
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const spaghettiIngredients = new MySet();
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spaghettiIngredients.addAll(['spaghetti', 'eggs', 'bacon', 'parmesan', 'pepper']);
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const recipes =
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[{
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name: 'Chicken Tikka Masala',
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ingredients: chickenIngredients
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},
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{
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name: 'Spaghetti Carbonara',
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ingredients: spaghettiIngredients
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}];
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// User's available ingredients
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const userIngredients = new MySet();
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userIngredients.addAll(['chicken', 'onion', 'garlic', 'ginger']);
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// Function to filter recipes
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function filterRecipes(recipes, userIngredients) {
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const filteredRecipes = [];
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for (const recipe of recipes) {
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if (userIngredients.isSubsetOf(recipe.ingredients)) {
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filteredRecipes.push({ name: recipe.name });
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}
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}
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return filteredRecipes;
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}
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// Filter recipes based on user's ingredients
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const matchingRecipes = filterRecipes(recipes, userIngredients);
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console.log(matchingRecipes);
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// [ { name: 'Chicken Tikka Masala' } ]
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// to see the output of this file use the command: node src/07-set/01-using-myset-class.js

‎src/07-set/02-using-set-class.js‎

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// src/07-set/02-using-set-class.js
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const article = {
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title: 'The importance of data structures in programming',
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content: '...',
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tags: new Set()
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tags: new Set(['programming', 'data structures', 'algorithms'])
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};
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// add tags
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article.tags.add('programming');
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article.tags.add('data structures');
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article.tags.add('algorithms');
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article.tags.add('programming');
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console.log(article.tags.size); // 3
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console.log(article.tags.has('data structures')); // true
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console.log(article.tags.has('algorithms')); // true
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console.log(article.tags.has('programming')); // true
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console.log(article.tags.has('javascript')); // false
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console.log(article.tags.values()); // ['programming', 'data structures', 'algorithms']
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// remove tags
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article.tags.delete('programming');
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article.tags.add('JavaScript');
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console.log(article.tags.values()); // ['data structures', 'algorithms', 'JavaScript']
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// to see the output of this file use the command: node src/07-set/02-using-set-class.js

‎src/07-set/leetcode/remove-duplicates-from-sorted-array.ts‎

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// https://leetcode.com/problems/remove-duplicates-from-sorted-array/description/
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/**
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* @param {number[]} nums
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* @return {number}
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*/
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export function removeDuplicates(nums: number[]): number {
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if (nums.length === 0) {
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return 0;
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}
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let i = 0;
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for (let j = 1; j < nums.length; j++) {
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if (nums[j] !== nums[i]) {
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i++;
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nums[i] = nums[j];
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}
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}
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return i + 1;
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}
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// resolve this problem using Set
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export function removeDuplicates2(nums: number[]): number {
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const set = new Set(nums);
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const arr = Array.from(set);
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for (let i = 0; i < arr.length; i++) {
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nums[i] = arr[i];
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}
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return arr.length;
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}
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// explain above solution
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// 1. create a set from the array
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// 2. create an array from the set
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// 3. copy the array to the original array
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// 4. return the length of the array
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// Time complexity: O(n)

‎src/07-set/set.js‎

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class MySet {
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#items = {};
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#size = 0;
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add(value) {
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if (!this.has(value)) {
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this.#items[value] = true; // mark the value as present
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this.#size++;
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return true;
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}
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return false;
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}
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addAll(values) {
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values.forEach(value => this.add(value));
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}
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delete(value) {
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if (this.has(value)) {
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delete this.#items[value];
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this.#size--;
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return true;
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}
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return false;
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}
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has(value) {
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return this.#items.hasOwnProperty(value);
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}
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values() {
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return Object.keys(this.#items);
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}
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get size() {
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return this.#size;
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}
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getSizeWithoutSizeProperty() {
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let count = 0;
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for (const key in this.#items) {
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if (this.#items.hasOwnProperty(key)) {
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count++;
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}
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}
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return count;
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}
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isEmpty() {
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return this.#size === 0;
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}
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clear() {
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this.#items = {};
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this.#size = 0;
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}
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union(otherSet) {
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const unionSet = new MySet();
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this.values().forEach(value => unionSet.add(value));
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otherSet.values().forEach(value => unionSet.add(value));
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return unionSet;
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}
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intersection(otherSet) {
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const intersectionSet = new MySet();
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const [smallerSet, largerSet] = this.size <= otherSet.size ? [this, otherSet] : [otherSet, this];
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smallerSet.values().forEach(value => {
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if (largerSet.has(value)) {
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intersectionSet.add(value);
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}
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});
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return intersectionSet;
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}
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difference(otherSet) {
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const differenceSet = new MySet();
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this.values().forEach(value => {
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if (!otherSet.has(value)) {
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differenceSet.add(value);
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}
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});
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return differenceSet;
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}
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isSubsetOf(otherSet) {
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if (this.size > otherSet.size) {
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return false;
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}
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return this.values().every(value => otherSet.has(value));
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}
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isSupersetOf(otherSet) {
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if (this.size < otherSet.size) {
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return false;
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}
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return otherSet.values().every(value => this.has(value));
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}
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toString() {
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return this.values().join(', ');
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}
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}
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module.exports = MySet;

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