Added Middle of LL function and tests

Author: 10kartik

Data-Structures/Linked-List/MiddleOfLinkedList.js

@@ -1,32 +1,27 @@
 /**
- * A LinkedList based solution for Detect a Cycle in a list
+ * A LinkedList based solution for finding middle node of linked list.
  * https://afteracademy.com/blog/middle-of-the-linked-list
  */
-
-function main () {
+class MiddleOfLL {
+  solution (head) {
   /*
     Problem Statement:
     Given the head of a singly linked list, return the middle node of the linked list.
     If there are two middle nodes, return the second middle node.
 
-    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/middle-of-the-linked-list/
     */
-  const head = '' // Reference to head is given in the problem. So please ignore this line
-  let fast = head
-  let slow = head
+    let fast = head
+    let slow = head
 
-  if (head.next == null) { return head }
+    if (head.next == null) { return head }
 
-  while (fast != null && fast.next != null) {
-    fast = fast.next.next
-    slow = slow.next
+    while (fast != null && fast.next != null) {
+      fast = fast.next.next
+      slow = slow.next
+    }
+    return slow
   }
-  return slow
 }
 
-main()
+export { MiddleOfLL }

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

@@ -0,0 +1,41 @@
+import { MiddleOfLL } from '../MiddleOfLinkedList'
+import { LinkedList } from '../SinglyLinkedList'
+
+describe('MiddleOfLinkedList', () => {
+  it('middle node Of linked list - even length ', () => {
+    const list = new LinkedList()
+    list.addFirst(1)
+    list.addLast(2)
+    list.addLast(3)
+    list.addLast(4)
+    list.addLast(5)
+    list.addLast(6)
+    list.addLast(7)
+
+    const MiddleNodeOfLinkedList = new MiddleOfLL().solution(list.headNode)
+    expect(MiddleNodeOfLinkedList.data).toEqual(4)
+  })
+
+  it('middle node of linked list - odd length ', () => {
+    const list = new LinkedList()
+    list.addFirst(10)
+    list.addLast(20)
+    list.addLast(30)
+    list.addLast(40)
+    list.addLast(50)
+    list.addLast(60)
+    list.addLast(70)
+    list.addLast(80)
+
+    const MiddleNodeOfLinkedList = new MiddleOfLL().solution(list.headNode)
+    expect(MiddleNodeOfLinkedList.data).toEqual(50)
+  })
+
+  it('middle node of linked list - length 1 ', () => {
+    const list = new LinkedList()
+    list.addFirst(100)
+
+    const MiddleNodeOfLinkedList = new MiddleOfLL().solution(list.headNode)
+    expect(MiddleNodeOfLinkedList.data).toEqual(100)
+  })
+})