refactor: RotateListRight.js and added tests

Data-Structures/Linked-List/RotateListRight.js

@@ -2,21 +2,13 @@
  * A LinkedList based solution for Rotating a List to the right by k places
  */
 
-function main () {
+function rotateListRight (head, k) {
   /*
   Problem Statement:
   Given a linked list, rotate the list to the right by k places, where k is non-negative.
 
-  Note:
-  * While Solving the problem in given link below, don't use main() function.
-  * Just use only the code inside main() function.
-  * The purpose of using main() function here is to avoid global variables.
-
   Link for the Problem: https://leetcode.com/problems/rotate-list/
   */
-  // Reference to both head and k is given in the problem. So please ignore below two lines
-  let head = ''
-  let k = ''
   let i = 0
   let current = head
   while (current) {
@@ -42,4 +34,4 @@ function main () {
   return head
 }
 
-main()
+export { rotateListRight }

Data-Structures/Linked-List/test/RotateListRight.test.js

@@ -0,0 +1,33 @@
+import { rotateListRight } from '../RotateListRight'
+import { Node } from '../SinglyLinkedList'
+
+describe('Rotate list by k steps', () => {
+  it('should shift every node by k steps towards right, shifts few tail nodes towards the start and change head of the list', () => {
+    // Case 0: when head is null
+    let headNode = rotateListRight(null, 0)
+    expect(headNode).toEqual(null)
+
+    // Creating list
+    headNode = new Node(10)
+    headNode.next = new Node(20)
+    headNode.next.next = new Node(30)
+    headNode.next.next.next = new Node(40)
+    headNode.next.next.next.next = new Node(50)
+
+    // Case 1: when k = 0 => List should be unaffected
+    headNode = rotateListRight(headNode, 0)
+    expect([headNode.data, headNode.next.data, headNode.next.next.data, headNode.next.next.next.data, headNode.next.next.next.next.data]).toEqual([10, 20, 30, 40, 50])
+
+    // Case 2: Rotate right by 2 steps
+    headNode = rotateListRight(headNode, 2)
+    expect([headNode.data, headNode.next.data, headNode.next.next.data, headNode.next.next.next.data, headNode.next.next.next.next.data]).toEqual([40, 50, 10, 20, 30])
+
+    // Case 3: Rotate right by 12 steps
+    headNode = rotateListRight(headNode, 12)
+    expect([headNode.data, headNode.next.data, headNode.next.next.data, headNode.next.next.next.data, headNode.next.next.next.next.data]).toEqual([20, 30, 40, 50, 10])
+
+    // Case 4: when k = length of the list = 5 => List should be unaffected
+    headNode = rotateListRight(headNode, 5)
+    expect([headNode.data, headNode.next.data, headNode.next.next.data, headNode.next.next.next.data, headNode.next.next.next.next.data]).toEqual([20, 30, 40, 50, 10])
+  })
+})