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Implemented queue (Closes CoffeelessProgrammer#4)
The following data structures have been implemented: Array, Hash Table, Stack, Queue, Binary Search Tree. All are available for import.
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‎Data-Structures/README.md

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## Core
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- [X] Arrays
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- [X] Hash Tables
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- [ ] Stacks
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- [ ] Queues
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- [X] Stacks
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- [X] Queues
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- [ ] Linked Lists
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- [X] Trees
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- [X] Binary Search Tree (BST)

‎Data-Structures/Sequential/Queue.ts

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import Node from '../Linked-Lists/NodeLL.ts';
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export default class Queue<T> {
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private last: Node<T> | null;
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private first: Node<T>| null;
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private length: number;
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constructor() {
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this.last = null;
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this.first = null;
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this.length = 0;
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}
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public getLength(): number {
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return this.length;
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}
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public peek(): T | null {
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return this.first?.getValue() || null;
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}
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public enqueue(value: T): boolean {
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const newNode = new Node(value);
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if (!this.last) { // If empty queue, initialize
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this.first = newNode;
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this.last = newNode;
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}
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else {
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this.last.setNext(newNode);
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this.last = this.last.getNext();
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}
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++this.length;
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return true;
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}
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public dequeue(): T | null {
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if (!this.first) return null; // Edge case: Empty queue
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if (this.length === 1) { // Edge case: Queue has 1 element, so a dequeue should reset the queue's state
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this.last = null; // Challenge: What is the state of each 'class field' after a dequeue when 1 element was remaining?
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}
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const value = this.first.getValue();
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this.first = this.first.getNext();
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--this.length;
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return value;
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}
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}
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function printQueue(queue: Queue<any>) {
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console.log(JSON.stringify(queue));
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}
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function printPeekQueue(queue: Queue<any>) {
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console.log('Peeking... Found', JSON.stringify(queue.peek()));
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}
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function printDequeue(queue: Queue<any>) {
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console.log('Dequeued:', JSON.stringify(queue.dequeue()));
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}
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//---------------------------------------------------------------------
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// ---------- MAIN PROGRAM ----------
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//---------------------------------------------------------------------
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if (import.meta.main) {
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const ATLA = new Queue<string>();
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printPeekQueue(ATLA);
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ATLA.enqueue('Sokka');
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ATLA.enqueue('Katara');
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printPeekQueue(ATLA);
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ATLA.enqueue('Aang');
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ATLA.enqueue('Appa');
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printQueue(ATLA);
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printDequeue(ATLA);
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printDequeue(ATLA);
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printDequeue(ATLA);
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printQueue(ATLA);
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printDequeue(ATLA);
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printQueue(ATLA);
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ATLA.enqueue('Zuko');
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ATLA.enqueue('Iroh');
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printQueue(ATLA);
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// RUN: deno run Data-Structures/Sequential/Queue.ts
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}
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// --------------------------- Terminal Output: ---------------------------
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// Peeking... Found null
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// Peeking... Found "Sokka"
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// {"last":{"value":"Appa","next":null},"first":{"value":"Sokka","next":{"value":"Katara","next":{"value":"Aang","next":{"value":"Appa","next":null}}}},"length":4}
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// Dequeued: "Sokka"
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// Dequeued: "Katara"
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// Dequeued: "Aang"
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// {"last":{"value":"Appa","next":null},"first":{"value":"Appa","next":null},"length":1}
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// Dequeued: "Appa"
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// {"last":null,"first":null,"length":0}
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// {"last":{"value":"Iroh","next":null},"first":{"value":"Zuko","next":{"value":"Iroh","next":null}},"length":2}

‎Data-Structures/Sequential/Stack.ts

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printStack(ATLA);
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// RUN: deno run Data-Structures/Sequential/Stack.ts
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}
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}
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// --------------------------- Terminal Output: ---------------------------
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// Peeking... Found null
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// Peeking... Found Katara
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// {"length":4,"values":["Sokka","Katara","Aang","Appa"]}
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// Popped: Appa
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// {"length":3,"values":["Sokka","Katara","Aang",null]}
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// Popped: Aang
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// Popped: Katara
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// Popped: Sokka
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// {"length":0,"values":[null,null,null,null]}
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// {"length":2,"values":["Zuko","Iroh",null,null]}

‎Data-Structures/Sequential/StackLL.ts

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printStack(ATLA);
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// RUN: deno run Data-Structures/Sequential/StackLL.ts
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}
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}
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// --------------------------- Terminal Output: ---------------------------
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// Peeking: null
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// Peeking: Katara
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// {"top":{"value":"Appa","next":{"value":"Aang","next":{"value":"Katara","next":{"value":"Sokka","next":null}}}},"bottom":{"value":"Sokka","next":null},"length":4}
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// Popped: Appa
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// {"top":{"value":"Aang","next":{"value":"Katara","next":{"value":"Sokka","next":null}}},"bottom":{"value":"Sokka","next":null},"length":3}
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// Popped: Aang
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// Popped: Katara
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// Popped: Sokka
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// {"top":null,"bottom":null,"length":0}
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// {"top":{"value":"Iroh","next":{"value":"Zuko","next":null}},"bottom":{"value":"Zuko","next":null},"length":2}

‎README.md

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### Data Structures
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- [X] Arrays
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- [X] Hash Tables
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- [ ] Stacks
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- [ ] Queues
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- [X] Stacks
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- [X] Queues
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- [ ] Linked Lists
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- [X] Trees
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- [ ] Graphs

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