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Commit 446bbab

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chapter 8: dictionary and hash table
1 parent fe6f722 commit 446bbab

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‎src/06-linked-list/linked-list_.js‎

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return this.#size;
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}
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forEach(callback) {
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let current = this.#head;
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let index = 0;
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while (current) {
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callback(current.data, index);
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current = current.next;
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index++;
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}
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}
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toString() {
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let current = this.#head;
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let objString = '';
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// src/08-dictionary-hash/01-using-dictionary-class.js
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const Dictionary = require('./dictionary');
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const translations = new Dictionary();
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// Add some translations - English to Portuguese
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translations.set("hello", "olá");
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translations.set("thank you", "obrigado");
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translations.set("book", "livro");
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translations.set("cat", "gato");
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translations.set("computer", "computador");
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// User interaction
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function translateWord(word) {
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if (translations.hasKey(word)) {
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const translation = translations.get(word);
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console.log(`The translation of "${word}" is "${translation}"`);
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} else {
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console.log(`Sorry, no translation found for "${word}"`);
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}
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}
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// Example usage
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translateWord("hello"); // Output: The translation of "hello" is "olá"
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translateWord("dog"); // Output: Sorry, no translation found for "dog"
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// Get all translations
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console.log("All translations:", translations.values());
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// All translations: [ 'olá', 'obrigado', 'livro', 'gato', 'computador' ]
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// Get all words
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console.log("All words:", translations.keys());
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// All words: [ 'hello', 'thank you', 'book', 'cat', 'computer' ]
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// Iterate through all translations
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translations.forEach((value, key) => {
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console.log(`${key}: ${value}`);
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});
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// to see the output of this file use the command: node src/08-dictionary-hash/01-using-dictionary-class.js
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// src/08-dictionary-hash/02-using-map-class.js
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const translations = new Map();
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// Add some translations - English to Portuguese
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translations.set("hello", "olá");
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translations.set("thank you", "obrigado");
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translations.set("book", "livro");
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translations.set("cat", "gato");
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translations.set("computer", "computador");
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// User interaction
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function translateWord(word) {
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if (translations.has(word)) {
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const translation = translations.get(word);
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console.log(`The translation of "${word}" is "${translation}"`);
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} else {
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console.log(`Sorry, no translation found for "${word}"`);
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}
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}
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// Example usage
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translateWord("hello"); // Output: The translation of "hello" is "olá"
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translateWord("dog"); // Output: Sorry, no translation found for "dog"
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// Get all translations
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console.log("All translations:", translations.values());
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// All translations: [ 'olá', 'obrigado', 'livro', 'gato', 'computador' ]
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// Get all words
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console.log("All words:", translations.keys());
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// All words: [ 'hello', 'thank you', 'book', 'cat', 'computer' ]
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// Iterate through all translations
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translations.forEach((value, key) => {
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console.log(`${key}: ${value}`);
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});
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// to see the output of this file use the command: node src/08-dictionary-hash/01-using-dictionary-class.js
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const privateData = new WeakMap();
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class Person {
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constructor(name, age) {
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this.name = name;
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this.age = age;
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privateData.set(this, { ssn: 'XXX-XX-XXXX', medicalHistory: [] });
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}
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getSSN() {
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return privateData.get(this)?.ssn;
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}
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}
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const alice = new Person("Penelope", 20);
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console.log(alice.name); // Penelope
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console.log(alice.getSSN()); // XXX-XX-XXXX
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// Try to access private data
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// src/08-dictionary-hash/04-using-hashmap-class.js
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const HashTable = require('./hash-table');
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const addressBook = new HashTable();
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// Add contacts
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addressBook.put('Gandalf', 'gandalf@email.com');
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addressBook.put('John', 'johnsnow@email.com');
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addressBook.put('Tyrion', 'tyrion@email.com');
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// Retrieve the hash code of a contact
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console.log(addressBook.hash('Gandalf')); // 19
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console.log(addressBook.hash('John')); // 29
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console.log(addressBook.hash('Tyrion')); // 16
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// Retrieve contacts
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console.log(addressBook.get('Gandalf')); // gandalf@email.com
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console.log(addressBook.get('Loiane')); // undefined
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// Remove contacts
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console.log(addressBook.remove('Gandalf')); // true
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console.log(addressBook.get('Gandalf')); // undefined
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// to see the output of this file use the command: node src/08-dictionary-hash/04-using-hashmap-class.js
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// src/08-dictionary-hash/05-hashmap-collision.js
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const HashTable = require('./hash-table');
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const addressBook = new HashTable();
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// Add contacts
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addressBook.put('Ygritte', 'ygritte@email.com');
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addressBook.put('Jonathan', 'jonathan@email.com');
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addressBook.put('Jamie', 'jamie@email.com');
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addressBook.put('Jack', 'jack@email.com');
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addressBook.put('Jasmine', 'jasmine@email.com');
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addressBook.put('Jake', 'jake@email.com');
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addressBook.put('Nathan', 'nathan@email.com');
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addressBook.put('Athelstan', 'athelstan@email.com');
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addressBook.put('Sue', 'sue@email.com');
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addressBook.put('Aethelwulf', 'aethelwulf@email.com');
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addressBook.put('Sargeras', 'sargeras@email.com');
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// Retrieve the hash code of a contact
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console.log(addressBook.hash('Ygritte'), '- Ygritte'); // 4
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console.log(addressBook.hash('Jonathan'), '- Jonathan'); // 5
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console.log(addressBook.hash('Jamie'), '- Jamie'); // 5
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console.log(addressBook.hash('Jack'), '- Jack'); // 7
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console.log(addressBook.hash('Jasmine'), '- Jasmine'); // 8
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console.log(addressBook.hash('Jake'), '- Jake'); // 9
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console.log(addressBook.hash('Nathan'), '- Nathan'); // 10
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console.log(addressBook.hash('Athelstan'), '- Athelstan'); // 7
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console.log(addressBook.hash('Sue'), '- Sue'); // 5
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console.log(addressBook.hash('Aethelwulf'), '- Aethelwulf'); // 5
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console.log(addressBook.hash('Sargeras'), '- Sargeras'); // 10
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console.log(addressBook.toString());
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// {4 => ygritte@email.com}
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// {5 => aethelwulf@email.com}
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// {7 => athelstan@email.com}
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// {8 => jasmine@email.com}
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// {9 => jake@email.com}
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// {10 => sargeras@email.com}
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// to see the output of this file use the command: node src/08-dictionary-hash/05-hashmap-collision.js

‎src/08-dictionary-hash/dictionary.js‎

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// src/08-dictionary-hash/dictionary.js
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class Dictionary {
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#items = {};
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#size = 0;
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hasKey(key) {
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return this.#items[this.#elementToString(key)] != null;
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}
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set(key, value) {
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if (key != null && value != null) {
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const tableKey = this.#elementToString(key);
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this.#items[tableKey] = 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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delete(key) {
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if (this.hasKey(key)) {
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delete this.#items[this.#elementToString(key)];
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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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get(key) {
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return this.#items[this.#elementToString(key)];
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}
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values() {
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return Object.values(this.#items);
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}
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keys() {
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return Object.keys(this.#items);
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}
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forEach(callbackFn) {
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for (const key in this.#items) {
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if (this.#items.hasOwnProperty(key)) {
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callbackFn(this.#items[key], key);
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}
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}
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}
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#elementToString(data) {
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if (typeof data === 'object' && data !== null) {
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return JSON.stringify(data);
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} else {
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return data.toString();
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}
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}
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}
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module.exports = Dictionary;
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// src/08-dictionary-hash/hash-table-linear-probing.js
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class HashTableLinearProbing {
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#table = [];
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#loseLoseHashCode(key) {
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if (typeof key !== 'string') {
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key = this.#elementToString(key);
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}
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const calcASCIIValue = (acc, char) => acc + char.charCodeAt(0);
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const hash = key.split('').reduce((acc, char) => calcASCIIValue, 0);
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return hash % 37; // mod to reduce the hash code
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}
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#djb2HashCode(key) {
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if (typeof key !== 'string') {
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key = this.#elementToString(key);
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}
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const calcASCIIValue = (acc, char) => (acc * 33) + char.charCodeAt(0);
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const hash = key.split('').reduce((acc, char) => calcASCIIValue, 5381);
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return hash % 1013;
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}
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hash(key) {
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return this.#loseLoseHashCode(key);
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}
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#elementToString(data) {
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if (typeof data === 'object' && data !== null) {
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return JSON.stringify(data);
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} else {
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return data.toString();
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}
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}
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put(key, value) {
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if (key != null && value != null) {
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let index = this.hash(key);
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// linear probing to find an empty slot
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while (this.#table[index] != null) {
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if (this.#table[index].key === key) {
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this.#table[index].value = value; // update existing key
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return true;
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}
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index++;
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index %= this.#table.length; // wrap around if end is reached
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}
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this.#table[index] = {key, value};
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return true;
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}
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return false;
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}
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get(key) {
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let index = this.hash(key);
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// Linear probing to search for the key
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while (this.#table[index] != null) {
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if (this.#table[index].key === key) {
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return this.#table[index].value;
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}
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index++;
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index %= this.#table.length;
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}
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return undefined; // key not found
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}
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remove(key) {
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let index = this.hash(key);
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while (this.#table[index] != null) {
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if (this.#table[index].key === key) {
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delete this.#table[index];
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this.#verifyRemoveSideEffect(key, index);
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return true;
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}
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index++;
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index %= this.#table.length;
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}
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return false; // key not found
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}
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#verifyRemoveSideEffect(key, removedPosition) {
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const size = this.#table.length;
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let index = removedPosition + 1;
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while (this.#table[index] != null) {
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const currentKey = this.#table[index].key;
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const currentHash = this.hash(currentKey);
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// check if the element should be repositioned
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if (currentHash <= removedPosition) {
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this.#table[removedPosition] = this.#table[index];
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delete this.#table[index];
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removedPosition = index;
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}
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index++;
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index %= size; // Wrap around if end is reached
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}
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}
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}

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