chore: add reverse to singly linked list

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 }

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

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+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)
+  })
+})