1 public static ListNode findElement(ListNode head, int k) { 2     if(k <= 0)    return null; 3      4     ListNode fast = head; 5     ListNode slow = head; 6      7     for(int i=0; i<k-1; i++) { 8         if(fast == null) return null; //edge case 9         fast = fast.next;10     }11     12     //fast = null13     if(fast == null) {14         return null;15     }16     17     while(fast.next != null) {18         fast = fast.next;19         slow = slow.next;20     }21     22     return slow;23 }