diff --git a/src/_DataStructures_/LinkedList/index.js b/src/_DataStructures_/LinkedList/index.js index 1704c3c4..e7964c01 100644 --- a/src/_DataStructures_/LinkedList/index.js +++ b/src/_DataStructures_/LinkedList/index.js @@ -8,32 +8,44 @@ class Node { class LinkedList { constructor() { this.head = null; + this.tail = null; + this.size = 0; } addAtBeginning(element) { this.head = new Node(element, this.head); + if (!this.tail) { + this.tail = this.head; + } + this.size += 1; + return this.head; } addAtEnd(element) { const node = new Node(element, null); + this.size += 1; if (!this.head) { this.head = node; - } else { - let address = this.head; - while (address.next) { - address = address.next; - } - address.next = node; + this.tail = node; + return node; } + this.tail.next = node; + this.tail = node; + return node; } removeFromBeginning() { if (!this.head) { return null; } + if (this.head.next === null) { + this.tail = this.head; + } const node = this.head; this.head = this.head.next; + this.size -= 1; + node.next = null; return node; } @@ -47,8 +59,11 @@ class LinkedList { address = address.next; } - const node = address.next; - address.next = null; + this.tail = address; + + const node = this.tail.next; + this.tail.next = null; + this.size -= 1; return node; } @@ -63,11 +78,7 @@ class LinkedList { if (!this.head) { return null; } - let address = this.head; - while (address.next) { - address = address.next; - } - return address; + return this.tail; } getAt(index) { @@ -104,8 +115,10 @@ class LinkedList { count -= 1; } - previous.next = new Node(element, previous.next); - return null; + const node = new Node(element, previous.next); + previous.next = node; + this.size += 1; + return node; } removeAt(index) { @@ -129,21 +142,19 @@ class LinkedList { const node = address; previous.next = address.next.next; + this.size -= 1; + node.next = null; return node; } length() { - let address = this.head; - let count = 0; - while (address) { - count += 1; - address = address.next; - } - return count; + return this.size; } delete() { this.head = null; + this.tail = this.head; + this.size = 0; } } diff --git a/src/_DataStructures_/Queue/Queue.test.js b/src/_DataStructures_/Queue/Queue.test.js index ebe7205c..bdbc6f26 100644 --- a/src/_DataStructures_/Queue/Queue.test.js +++ b/src/_DataStructures_/Queue/Queue.test.js @@ -12,23 +12,24 @@ describe('Data Structure : Queue', () => { queue = new Queue(); }); - it('Should add() element to a queue', () => { - queue.add(5); - expect(queue.data).toEqual([5]); + it('Should add element to a queue', () => { + queue.enqueue(5); + expect(queue.peek()).toEqual(5); }); - it('Should remove() an element from the queue', () => { - queue.add(2); - queue.add(3); + it('Should dequeue() an element from the queue', () => { + queue.enqueue(2); + queue.enqueue(3); - expect(queue.remove()).toEqual(2); - expect(queue.data).toEqual([3]); + expect(queue.dequeue()).toEqual(2); + expect(queue.peek()).toEqual(3); + expect(queue.length()).toEqual(1); }); describe('peek()', () => { beforeEach(() => { - queue.add(2); - queue.add(5); + queue.enqueue(2); + queue.enqueue(5); }); it('Should return the elemet to be removed using peek()', () => { @@ -37,21 +38,21 @@ describe('Data Structure : Queue', () => { it('Should not remove the element', () => { expect(queue.peek()).toEqual(2); - expect(queue.remove()).toEqual(2); + expect(queue.dequeue()).toEqual(2); }); }); it('Should maintain the order of elements', () => { // first in first out - queue.add(2); - queue.add(1); - queue.add(4); - queue.add(3); - - expect(queue.remove()).toEqual(2); - expect(queue.remove()).toEqual(1); - expect(queue.remove()).toEqual(4); - expect(queue.remove()).toEqual(3); + queue.enqueue(2); + queue.enqueue(1); + queue.enqueue(4); + queue.enqueue(3); + + expect(queue.dequeue()).toEqual(2); + expect(queue.dequeue()).toEqual(1); + expect(queue.dequeue()).toEqual(4); + expect(queue.dequeue()).toEqual(3); }); }); }); diff --git a/src/_DataStructures_/Queue/QueueUsingArray.js b/src/_DataStructures_/Queue/QueueUsingArray.js new file mode 100644 index 00000000..99d1861c --- /dev/null +++ b/src/_DataStructures_/Queue/QueueUsingArray.js @@ -0,0 +1,20 @@ +class Queue { + constructor() { + this.data = []; + } + + add(element) { + // add element to the start of the data + return this.data.unshift(element); + } + + peek() { + return this.data[this.data.length - 1]; + } + + remove() { + return this.data.pop(); + } +} + +module.exports = Queue; diff --git a/src/_DataStructures_/Queue/index.js b/src/_DataStructures_/Queue/index.js index d51bcab0..9056c130 100644 --- a/src/_DataStructures_/Queue/index.js +++ b/src/_DataStructures_/Queue/index.js @@ -1,20 +1,57 @@ -class Queue { +const { LinkedList: SinglyLinkedLists } = require('../LinkedList'); + +class Queue extends SinglyLinkedLists { constructor() { - this.data = []; + super(); + this.NotAllowed = 'Not Allowed'; + } + + enqueue(data) { + return this.addAtEnd(data); } - add(element) { - // add element to the start of the data - return this.data.unshift(element); + dequeue() { + const node = this.removeFromBeginning(); + return node ? node.data : node; } peek() { - return this.data[this.data.length - 1]; + const node = this.getFirst(); + return node ? node.data : node; + } + + length() { + return this.size; + } + + destroy() { + this.delete(); + } + + /** Override and throw error for other LL methods */ + addAtBeginning() { + throw new Error(this.NotAllowed); + } + + addAt() { + throw new Error(this.NotAllowed); + } + + removeFromEnd() { + throw new Error(this.NotAllowed); + } + + getLast() { + throw new Error(this.NotAllowed); + } + + getAt() { + throw new Error(this.NotAllowed); } - remove() { - return this.data.pop(); + removeAt() { + throw new Error(this.NotAllowed); } } -module.exports = Queue; \ No newline at end of file +module.exports = Queue; diff --git a/src/_DataStructures_/Queue/weave/index.js b/src/_DataStructures_/Queue/weave/index.js index 94d1d660..5a6da801 100644 --- a/src/_DataStructures_/Queue/weave/index.js +++ b/src/_DataStructures_/Queue/weave/index.js @@ -4,12 +4,12 @@ function weaveQueues(first, second) { const weaved = new Queue(); while (first.peek() || second.peek()) { - if (first.peek() !== undefined) { - weaved.add(first.remove()); + if (first.peek()) { + weaved.enqueue(first.dequeue()); } - if (second.peek() !== undefined) { - weaved.add(second.remove()); + if (second.peek()) { + weaved.enqueue(second.dequeue()); } } return weaved; diff --git a/src/_DataStructures_/Queue/weave/weave.test.js b/src/_DataStructures_/Queue/weave/weave.test.js index da307f36..05c43ec0 100644 --- a/src/_DataStructures_/Queue/weave/weave.test.js +++ b/src/_DataStructures_/Queue/weave/weave.test.js @@ -10,18 +10,18 @@ describe('Weave two queues using weaveQueues()', () => { const q1 = new Queue(); const q2 = new Queue(); - q1.add('Hello'); - q2.add(1); - q1.add('World'); - q2.add(2); - q2.add(3); + q1.enqueue('Hello'); + q2.enqueue(1); + q1.enqueue('World'); + q2.enqueue(2); + q2.enqueue(3); const q3 = weaveQueues(q1, q2); - expect(q3.remove()).toEqual('Hello'); - expect(q3.remove()).toEqual(1); - expect(q3.remove()).toEqual('World'); - expect(q3.remove()).toEqual(2); - expect(q3.remove()).toEqual(3); + expect(q3.dequeue()).toEqual('Hello'); + expect(q3.dequeue()).toEqual(1); + expect(q3.dequeue()).toEqual('World'); + expect(q3.dequeue()).toEqual(2); + expect(q3.dequeue()).toEqual(3); }); });

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