Sep 15, 2022 · Sep 15, 2022 · Sep 15, 2022 · Sep 15, 2022
diff --git a/Data-Structures/Linked-List/CycleDetection.js b/Data-Structures/Linked-List/CycleDetection.js
diff --git a/Data-Structures/Linked-List/test/CycleDetection.test.js b/Data-Structures/Linked-List/test/CycleDetection.test.js
Original file line number	Diff line number	Diff line change
		@@ -1,32 +1,24 @@
		/**
	* A LinkedList based solution for Detect a Cycle in a list
	* A LinkedList based solution for Detecting a Cycle in a list.
		* https://en.wikipedia.org/wiki/Cycle_detection
		*/

	function main () {
	function detectCycle (head) {
		/*
		Problem Statement:
		Given head, the head of a linked list, determine if the linked list has a cycle in it.

	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/linked-list-cycle/
		*/
	const head = '' // Reference to head is given in the problem. So please ignore this line
	let fast = head
	let slow = head
	if (!head) { return false }

	while (fast != null && fast.next != null && slow != null) {
	let slow = head
	let fast = head.next
	while (fast && fast.next) {
	if (fast === slow) { return true }
		fast = fast.next.next
		slow = slow.next
	if (fast === slow) {
	return true
	}
		}
		return false
		}

	main()
	export { detectCycle }
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,31 @@
	import { detectCycle } from '../CycleDetection'
	import { Node } from '../SinglyLinkedList'

	describe('Detect Cycle', () => {
	it('should detect loop and return true', () => {
	// Creating list and making a loop
	const 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 = headNode
	expect(detectCycle(headNode)).toEqual(true)
	})

	it('should not detect a loop and return false', () => {
	// Case 0: When head is null, there is no loop.
	expect(detectCycle(null)).toEqual(false)
	const headNode = new Node(10)

	// Case 1: List with single node doesn't have any loop
	expect(detectCycle(headNode)).toEqual(false)

	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 2: List not having any loops
	expect(detectCycle(headNode)).toEqual(false)
	})
	})