2.6 Given a circular linked list, implement an algorithm which returns the node at the beginning of the loop. DEFINITION Circular linked list: A (corrupt) linked list in which a node's next pointer points to an earlier node, so as to make a loop in the linked list. EXAMPLE Input:A ->B->C->D->E-> C[thesameCasearlier] Output:C

2.6 detectCycle

ListNode {
    int val;
    ListNode next;
    ListNode(int val) {
        this.val = val;
        next = null;
    }
}

public ListNode detectCycle(ListNode head) {
    // Check the edge case when there are only 2 or 3 nodes
    if (head == null || head.next == null || head.next.next == null) {
        return null;
    }
        
    ListNode slow = head;
    ListNode fast = head;
    while (fast.next != null && fast.next.next != null) {
        slow = slow.next;
        fast = fast.next.next;
        if (slow == fast) {
            break;
        }
    }
        
    if (slow != fast) {
        return null;
    }
        
    slow = head;
    while (slow != fast) {
        slow = slow.next;
        fast = fast.next;
    }
        
    return slow;
}