/*

public class ListNode {

    int val;

    ListNode next = null;

    ListNode(int val) {

        this.val = val;

    }

}*/

public class Solution {

    public ListNode ReverseList(ListNode head) {

        ListNode newHead = new ListNode(-1);

        while(head != null){

            ListNode tmp = head.next;

            head.next = newHead.next;

            newHead.next = head;

            head = tmp;

        }

        return newHead.next;

    }

}

public ListNode ReverseList(ListNode head) {

    if (head == null || head.next == null)

        return head;

    ListNode next = head.next;

    head.next = null;

    ListNode newHead = ReverseList(next);

    next.next = head;

    return newHead;

}