diff --git a/Data-Structures/Linked-List/ReverseSinglyLinkedList.js b/Data-Structures/Linked-List/ReverseSinglyLinkedList.js new file mode 100644 index 0000000000..db4e7ef6d6 --- /dev/null +++ b/Data-Structures/Linked-List/ReverseSinglyLinkedList.js @@ -0,0 +1,16 @@ +/** A LinkedList based solution to reverse a number +Problem Statement: Given a number such that each of its digit is stored in a singly linked list. Reverse the linked list and return the head of the linked list Link for the Problem: https://leetcode.com/problems/reverse-linked-list/ */ +class ReverseSinglyLinkedList { + solution (head) { + let prev = null + let next = null + while (head) { + next = head.next + head.next = prev + prev = head + head = next + } + return prev + }; +} +export { ReverseSinglyLinkedList } diff --git a/Data-Structures/Linked-List/SinglyLinkedList.js b/Data-Structures/Linked-List/SinglyLinkedList.js index d55e0b14b8..605ede4013 100644 --- a/Data-Structures/Linked-List/SinglyLinkedList.js +++ b/Data-Structures/Linked-List/SinglyLinkedList.js @@ -274,6 +274,20 @@ class LinkedList { log () { console.log(JSON.stringify(this.headNode, null, 2)) } + + // Method to reverse the LinkedList + reverse () { + let head = this.headNode + let prev = null + let next = null + while (head) { + next = head.next + head.next = prev + prev = head + head = next + } + this.headNode = prev + }; } export { Node, LinkedList } diff --git a/Data-Structures/Linked-List/test/ReverseSinglyLinkedList.test.js b/Data-Structures/Linked-List/test/ReverseSinglyLinkedList.test.js new file mode 100644 index 0000000000..847026db89 --- /dev/null +++ b/Data-Structures/Linked-List/test/ReverseSinglyLinkedList.test.js @@ -0,0 +1,14 @@ +import { ReverseSinglyLinkedList } from '../ReverseSinglyLinkedList' +import { Node } from '../SinglyLinkedList' +describe('ReverseSinglyLinkedList', () => { + it('Reverse a Number Represented as Linked List', () => { + const headNode = new Node(3) + headNode.next = new Node(4) + headNode.next.next = new Node(1) + const expected = new Node(1) + expected.next = new Node(4) + expected.next.next = new Node(3) + const reverseSinglyLinkedList = new ReverseSinglyLinkedList() + expect(reverseSinglyLinkedList.solution(headNode)).toEqual(expected) + }) +}) diff --git a/Data-Structures/Linked-List/test/SinglyLinkedList.test.js b/Data-Structures/Linked-List/test/SinglyLinkedList.test.js index 764cac7aa9..a04d06ba15 100644 --- a/Data-Structures/Linked-List/test/SinglyLinkedList.test.js +++ b/Data-Structures/Linked-List/test/SinglyLinkedList.test.js @@ -247,4 +247,10 @@ describe('SinglyLinkedList', () => { headNode.rotateListRight(5) expect(headNode.get()).toEqual([20, 30, 40, 50, 10]) }) + + it('Reverse a Linked List', () => { + const list = new LinkedList([4, 3, 1]) + list.reverse() + expect(list.get()).toEqual([1, 3, 4]) + }) })