Lecture 201:- Let's Code to Check LOOP

To check if a linked list contains a loop, you can use the Floyd's cycle-finding algorithm, also known as the "tortoise and hare" algorithm. It involves using two pointers that move through the linked list at different speeds. If there is a loop, the two pointers will eventually meet.

Here's a Java implementation to check if a linked list contains a loop:

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class ListNode {    int val;    ListNode next;    ListNode(int val) {        this.val = val;        this.next = null;    } } public class LinkedListLoop {    public boolean hasCycle(ListNode head) {        if (head == null || head.next == null) {            return false;        }        ListNode slow = head;        ListNode fast = head.next;        while (slow != fast) {            if (fast == null || fast.next == null) {                return false;            }            slow = slow.next;            fast = fast.next.next;        }        return true;    }    public static void main(String[] args) {        LinkedListLoop solution = new LinkedListLoop();        // Create a linked list with a loop        ListNode head = new ListNode(1);        head.next = new ListNode(2);        head.next.next = new ListNode(3);        head.next.next.next = new ListNode(4);        head.next.next.next.next = head; // Create the loop        System.out.println("Does the linked list have a loop? " + solution.hasCycle(head));    } }

In the hasCycle method, we use two pointers slow and fast, where slow moves one step at a time and fast moves two steps at a time through the linked list. If there is a loop, the fast pointer will eventually catch up to the slow pointer, indicating the presence of a cycle. If there is no loop, the fast pointer will reach the end of the list and return false.

In the main method, we demonstrate the function with an example linked list containing a loop. The output will be true since the linked list contains a cycle.