/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
public class Solution {
// public ListNode reverseList(ListNode head) {
// ListNode prev = null;
// while (head != null) {
// ListNode temp = head.next;
// head.next = prev;
// prev = head;
// head = temp;
// }
// return prev;
// }
public ListNode reverseList(ListNode head) {
if (head == null || head.next == null) {
return head;
}
ListNode second = head.next;
head.next = null;
ListNode rest = reverseList(second);
second.next = head;
return rest;
}
}