public class Solution {
    public boolean hasCycle(ListNode head) {
        if(head == null){
             
            return false;
        }
         
        ListNode l1 = head;
        ListNode l2 = head;
        while(l2!=null && l2.next!=null){
             
            l2 = l2.next.next;
            l1 = l1.next;
            if(l1 == l2){
                 
            return true;
            } 
        }
        return false;
    }
}