1public class LinkedList {
2
3    static Node head;
4
5    static class Node {
6        int data;
7        Node next;
8
9        Node(int d) {
10            data = d;
11            next = null;
12        }
13    }
14
15    // Function to detect and return the starting node of a cycle in the linked list
16    static Node detectCycle(Node head) {
17        if (head == null || head.next == null) {
18            return null;
19        }
20
21        Node slow = head;
22        Node fast = head;
23        while (fast != null && fast.next != null) {
24            slow = slow.next;
25            fast = fast.next.next;
26
27            // If slow and fast pointers meet, there is a cycle
28            if (slow == fast) {
29
30                // Reset slow pointer to head
31                slow = head;
32
33                /* Move both slow and fast pointers one node at a time
34                   until they meet at the starting node of the cycle */
35                while (slow != fast) {
36                    slow = slow.next;
37                    fast = fast.next;
38                }
39                return slow;
40            }
41        }
42
43        // If no cycle is present in the linked list
44        return null;
45    }
46
47    public static void main(String[] args) {
48        LinkedList list = new LinkedList();
49
50        // Create a linked list with a cycle
51        list.head = new Node(1);
52        list.head.next = new Node(2);
53        list.head.next.next = new Node(3);
54        list.head.next.next.next = new Node(4);
55        list.head.next.next.next.next = new Node(5);
56        list.head.next.next.next.next.next = list.head.next;
57
58        Node cycleStart = detectCycle(head);
59        if (cycleStart != null) {
60            System.out.println("Cycle found at node: " + cycleStart.data);
61        } else {
62            System.out.println("No cycle found in the linked list");
63        }
64    }
65}