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daviskamaudaviskamau
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‎system-design-frontend/Classes/LRU/index.js‎

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class LRUCache {
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constructor(capacity) {
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this.map = new Object();
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this.size = 0; // to track the total number of items which should not be more than capacity
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this.store = new DoublyLinkedList();
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this.capacity = capacity; // max size of the cache
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}
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get(key) {
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// if key is not present
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if (!this.map[key]) {
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return -1;
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}
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// if key is present , remove the node from its position and put it at the tail as most recently used
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const targetNode = this.map[key];
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targetNode.remove();
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this.map[targetNode.key] = this.store.append(targetNode.key, targetNode.val);
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return targetNode.val;
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}
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put(key, val) {
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// if the node is present in cache
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if (this.map[key]) {
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const targetNode = this.map[key];
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targetNode.remove();
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this.size -= 1;
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}
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// in either case, a new node is created and put as the most recently used at the tail
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const newNode = this.store.append(key, val);
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this.map[key] = newNode;
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this.size += 1;
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if (this.size > this.capacity) {
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const firstNode = this.store.removeFirst(); // remove the least recently used
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delete this.map[firstNode.key];
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this.size -= 1;
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}
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}
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}
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// Creating a node class of doubly LL
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class ListNode {
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constructor(key = null, val = null) {
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this.key = key;
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this.val = val;
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this.prev = null;
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this.next = null;
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}
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remove() {
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this.prev.next = this.next;
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this.next.prev = this.prev;
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this.prev = null;
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this.next = null;
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}
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}
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// Creating a doubly linked list
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class DoublyLinkedList {
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constructor() {
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this.head = new ListNode();
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this.tail = new ListNode();
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this.head.next = this.tail;
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this.tail.prev = this.head;
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}
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append(key, val) {
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const newNode = new ListNode(key, val);
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const lastNode = this.tail.prev;
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lastNode.next = newNode;
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newNode.prev = lastNode;
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this.tail.prev = newNode;
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newNode.next = this.tail;
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return newNode;
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}
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removeFirst() {
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const firstNode = this.head.next;
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firstNode.remove();
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return firstNode;
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}
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}

‎system-design-frontend/Classes/Library Management System/index.js‎

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const BookStatus = {
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AVAILABLE: 'AVAILABLE',
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LOANED: 'LOANED',
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LOST: 'LOST'
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};
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const AccountStatus = {
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ACTIVE: 'ACTIVE',
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INACTIVE: 'INACTIVE',
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CLOSED: 'CLOSED',
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BLACKLISTED: 'BLACKLISTED'
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};
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class LibraryCard {
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constructor() {
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this.cardNumber = this.generateRandomCardNumber();
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this.barCode = this.generateBarcode();
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this.issuedAt = new Date();
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this.isActive = true;
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}
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setActive(status) {
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this.isActive = status;
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}
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}
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class Account {
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constructor(name, email, password, status) {
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this.userId = this.geenrateRandomeID();
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this.name = name;
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this.email = email;
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this.password = password;
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this.status = status;
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this.libraryCard = new LibraryCard();
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}
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login(email, password) {
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if (email === this.email && this.password === password) {
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console.log('Logged IN');
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this.status = AccountStatus.ACTIVE;
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}
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else {
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console.log('Wrong Credentials')
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}
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}
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logout() {
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this.status = AccountStatus.INACTIVE;
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};
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resetPassword(oldPassword, newPassword) {
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if (oldPassword === this.password) {
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this.password = newPassword;
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}
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else {
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alert('Old Password does not match')
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}
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};
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closeAccount() {
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this.status = AccountStatus.CLOSED;
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}
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}
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class Member extends Account {
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constructor() {
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this.booksBorrowed = 0;
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this.searchBook = new Search();
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this.dateOfMemeberShip = new Date();
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}
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payFine(amount) {
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}
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checkForFine() {
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}
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}
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class Librarian extends Account {
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constructor() {
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this.issueService = new BookIssueService();
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this.searchBook = new Search();
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}
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addBook(book);
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deleteBook(book_id);
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// return the updated book
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updateBook(book);
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blockMember(member);
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unBlockMember(member);
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cancelMembership(member);
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}
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class Search {
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getBookByTitle(title) {
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return this.callAPI(title)
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};
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getBookByAuthor(author) {
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return this.callAPI(author)
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};
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getBookByCateogry(bookType) {
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return this.callAPI(bookType)
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};
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}
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class Book {
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constructor(title, author, category, shelf, floor, status) {
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this.bookId = this.geenrateRandomeID();
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this.title = title;
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this.author = author;
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this.category = category;
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this.location = new Location(shelf, floor);
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this.status = status;
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}
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setBookStatus(status) {
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this.status = status;
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}
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setBorrowDate(date) {
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this.borrowDate = date;
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this.setDueDate(this.borrowDate + 15)
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}
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setDueDate(dueDate) {
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this.dueDate = dueDate;
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}
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}
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class Location {
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constructor(shelf, floor) {
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this.shelfNo = shelf;
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this.floorNo = floor;
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}
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getLocation() {
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}
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}
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class BookIssueService {
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calculateFine(days, user, book) {
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};
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collectFine(user, days) {
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};
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issueBook(book, user) {
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return dueDate
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};
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renewBook(book, user) {
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return dueDate;
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};
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returnBook(book, user) {
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};
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}
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class BookIssueDetail {
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constructor(book, startDate, user) {
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this.book = book;
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this.startDate = startDate;
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this.user = user;
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this.dueDate = startDate + 15;
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}
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}

‎system-design-frontend/Classes/MusicPlayer/MusicPlayer.js‎

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// https://prakhargurawa.medium.com/design-a-music-player-with-shuffle-functionality-f9d6f53ff028
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class MusicPlayer {
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constructor() {
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this.totalSongCount = 0;
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this.musicList = [];
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this.musicQ = [];
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this.random = 0;
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this.addSong = this.addSong.bind(this);
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this.playRandomSong = this.playRandomSong.bind(this);
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this.playSong = this.playSong.bind(this);
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this.closeMusicPlayer = this.closeMusicPlayer.bind(this);
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this.printList = this.printList.bind(this);
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}
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addSong(song) {
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console.log(song.songName);
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this.musicList.splice(this.totalSongCount, 0, song);
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this.totalSongCount++;
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}
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playSong(id, addToQ) {
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for (let i = 0; i < this.totalSongCount; i++) {
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let song = this.musicList[i];
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console.log("Playing song " + song.songName);
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if (song.id === id) {
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if (addToQ) this.musicQ.push(song);
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this.musicList.splice(i, 1);
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this.musicList.push(song);
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this.totalSongCount--;
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if (this.totalSongCount < 0) {
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this.totalSongCount = this.musicList.length;
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}
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}
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}
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for (let i = this.totalSongCount; i < this.musicList.length; i++) {
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let song = this.musicList[i];
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if (song.id === id) {
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if (addToQ) this.musicQ.push(song);
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}
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}
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}
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playRandomSong() {
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this.random = Math.floor(Math.random() * this.totalSongCount);
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let song = this.musicList[this.random];
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console.log("Playing song " + song.songName + " at index " + this.random);
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this.musicQ.push(song);
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this.musicList.splice(this.random, 1);
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this.musicList.push(song);
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this.totalSongCount--;
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if (this.totalSongCount < 0) {
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this.totalSongCount = this.musicList.length;
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}
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this.printList();
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}
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closeMusicPlayer() {
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console.log("Closing Music Player");
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this.musicQ = [];
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this.totalSongCount = this.musicList.length;
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}
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printList() {
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console.log("Total Songs Count", this.totalSongCount);
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console.log(
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"MusicList :",
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this.musicList.map((ele) => `${ele.id}-${ele.songName}`)
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);
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console.log(
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"Music Queue: ",
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this.musicQ.map((ele) => `${ele.id}-${ele.songName}`)
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);
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}
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}
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export default MusicPlayer;

‎system-design-frontend/Classes/MusicPlayer/Song.js‎

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class Song {
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constructor(id, songName, singerName, genre) {
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this.id = id;
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this.songName = songName;
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this.singerName = singerName;
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this.genre = genre;
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}
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}
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export default Song;

‎system-design-frontend/Classes/MusicPlayer/index.js‎

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import MusicPlayer from "./MusicPlayer";
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import Song from "./Song";
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let songs = [
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new Song(1, "Levitating", "Dua Lipa", "Hollywood"),
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new Song(2, "Love you Zindagi", "Alia Bhatt", "Bollywood"),
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new Song(3, "Dil", "Villain", "Bollywood"),
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new Song(4, "I Like me better", "Selena", "Hollywood"),
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new Song(5, "LoveStory", "Taylor", "Hollywood")
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];
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let musicPlayer = new MusicPlayer();
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songs.forEach((song) => musicPlayer.addSong(song));
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musicPlayer.printList();
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[1, 2, 3, 4, 5, 6, 7].forEach((_) => musicPlayer.playRandomSong());
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musicPlayer.playSong(2, false);

‎system-design-frontend/Classes/SnakeAndLadder/Board.js‎

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class Board {
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constructor(size) {
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this.size = size;
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}
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}
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export default Board;

‎system-design-frontend/Classes/SnakeAndLadder/Dice.js‎

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class Dice {
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constructor() {
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this.maxNumber = 6
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}
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rollDice() {
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return Math.floor(Math.random() * this.maxNumber);
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}
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}
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export default Dice;

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