index.html

<script>
		const xhr = new XMLHttpRequest();
		xhr.open('GET', '/users');
		xhr.onload = () => {
			if(xhr.status === 200){
				const data = JSON.parse(xhr.responseText);
				let html = '';
				for (let el of data){
					html += `<p>${el.name}</p>`;
				}

				document.getElementById('dataContainer').innerHTML = html;
			}
		};

		xhr.send();
</script>

<script type="text/javascript">
	
	/*
	1. Hare reaches the end = no duplicates.

	The nodes with the value 7 have different next values, so there is no way for the pointers to loop back to a previously visited node. As a result, the findDuplicate function will return null because it will not find a cycle in the linked list.

	One option is to use a hash table to store the values of the nodes as you iterate through the linked list. If you encounter a value that is already in the hash table, it means that you have found a duplicate element.

	*/

class LinkedList{
	constructor(head = null){
		this.head = head;
	}

	appendNode(newNode){
		let node = this.head;
		if(node === null){
			this.head = newNode;
			return;
		}

		while(node.next){
			node = node.next;
		}

		node.next = newNode;
	}

	printList(){
		let node = this.head;
		process.stdout.write('HEAD->');
		while(node){
			process.stdout.write(node.value + "->");
			node = node.next;
		}

		console.log("NULL");
	}

	
	findDuplicateCycle(){
		let slow = this.head;
		let fast = this.head;
		while(fast !== null && fast.next !== null){
			slow = slow.next;
			fast = fast.next.next;
			if(fast === slow){
				break;
			}
		}

		if(fast === null || fast.next === null){
			return null;
		}

		slow = this.head;
		while(slow !== fast){
			slow = slow.next;
			fast = fast.next;
		}

		return slow;
	}
}

class Node{
	constructor(value){
		this.value = value;
		this.next = null;
	}
}

const myList = new LinkedList();
myList.appendNode(new Node(1));
myList.appendNode(new Node(7));
myList.appendNode(new Node(5));
myList.appendNode(new Node(7));
myList.appendNode(new Node(9));

myList.printList();
myList.findDuplicateCycle();

</script>

node *find_loop(node *head)
{
	node *p1;
	node *p2;

	if (head == NULL)
		return (NULL);
	p1 = head;
	p2 = head;
	while (p2->next != NULL && p2->next->next != NULL)
	{
		p1 = p1->next;
		p2 = p2->next->next;
		if (p1 == p2)
		{
			p1 = head;
			while (p1 != p2)
			{
				p1 = p1->next;
				p2 = p2->next;
			}
			return (p2);