/**
 * Definition for ListNode.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int val) {
 *         this.val = val;
 *         this.next = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param head: The first node of linked list.
     * @return: True if it has a cycle, or false
     */
    public boolean hasCycle(ListNode head) {
        if (head == null || head.next == null){
            return false;
        }
        ListNode first = head;
        ListNode second = head;
        while (first != null && second != null && second.next != null){
            second = second.next.next;
            first = first.next;
            if (first == second){
                return true;
            }
        }
        return false;
    }
}

public class Solution {
    ListNode nthToLast(ListNode head, int n) {
       ListNode first = head;
       ListNode end = head;
       for (int i=0;i<n;i++){
           end = end.next;
       }
       while(end != null){
           end =  end.next;
           first = first.next;
       }
       return first;
    }
}