Doubly Linked List 😉

Author: deadcoder0904

examples/datastructures/doubly-linked-list.js

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+class Node {
+	constructor(data) {
+		this.data = data;
+		this.prev = null;
+		this.next = null;
+	}
+}
+
+class LinkedList {
+	constructor() {
+		this.head = new Node("head");
+	}
+
+	find(data) {
+		let temp = this.head;
+		while(temp.data != data)
+			temp = temp.next;
+		return temp;
+	}
+
+	findLast() {
+		let temp = this.head;
+		while(temp.next != null)
+			temp = temp.next;
+		return temp;
+	}
+
+	printList() {
+		let temp = this.head;
+		if(temp.next == null)
+			return "The Linked List is Empty";
+		let str = "";
+		while(temp.next != null) {
+			str += temp.next.data + " -> ";
+			temp = temp.next;
+		}
+		str += "NULL\n";
+		return str;
+	}
+
+	printListReverse() {
+		let temp = this.findLast();
+		if(temp.prev == null)
+			return "The Linked List is Empty";
+		let str = "";
+		while(temp.prev != null) {
+			str += temp.data + " -> ";
+			temp = temp.prev;
+		}
+		str += "NULL\n";
+		return str;
+	}
+
+	insertAfter(data,currData) {
+		const newNode = new Node(data);
+		let curr = this.find(currData);
+		newNode.next = curr.next;
+		newNode.prev = curr;
+		curr.next = newNode;
+	}
+
+	remove(data) {
+		const curr = this.find(data);
+		if(curr.next != null) {
+			curr.prev.next = curr.next;
+			curr.next.prev = curr.prev;
+			curr.prev = null;
+			curr.next = null;
+		}
+		else this.head.next = null;
+	}
+}
+
+module.exports = LinkedList;

test/datastructures/doubly-linked-list.test.js

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+const expect = require('chai').expect;
+const DoublyLinkedList = require('../../examples/datastructures/doubly-linked-list');
+
+describe('=> DOUBLY LINKED LIST', function() {
+	let names;
+	before(function () {
+		names = new DoublyLinkedList();
+	});
+
+	it('should create an Empty Linked List', function(done) {
+		expect(names.head.data).to.equal("head");
+		done();
+	});
+
+	it('should print an Empty Linked List', function(done) {
+		expect(names.printList()).to.equal("The Linked List is Empty");
+		done();
+	});
+
+	it('should insert into a Linked List', function(done) {
+		names.insertAfter(1,"head");
+		names.insertAfter(2, 1);
+		names.insertAfter(3, 2);
+		names.insertAfter(4, 3);
+		expect(names.printList()).to.equal("1 -> 2 -> 3 -> 4 -> NULL\n");
+		expect(names.printListReverse()).to.equal("4 -> 3 -> 2 -> 1 -> NULL\n");
+		done();
+	});
+
+	it('should remove element from a Linked List', function(done) {
+		names.remove(1);
+		expect(names.printList()).to.equal("2 -> 3 -> 4 -> NULL\n");
+		expect(names.printListReverse()).to.equal("4 -> 3 -> 2 -> NULL\n");
+		done();
+	});
+
+	describe('=> clear', function() {
+		it('should clear the Linked List', function(done) {
+			names.remove(2);
+			names.remove(3);
+			names.remove(4);
+			expect(names.printList()).to.equal("The Linked List is Empty");
+			done();
+		});
+	});
+
+});