/* public class ListNode { int val; ListNode next = null; ListNode(int val) { this.val = val; } }*/ public class Solution { public ListNode ReverseList(ListNode head) { if(head==null||head.next==null){ return head; } ListNode pre = null; ListNode next =null; while(head!=null){ next =head.next; head.next=pre; pre =head; head= next; } return pre; } }