反转链表

题目描述

输入一个链表，反转链表后，输出新链表的表头。

 1 /*
 2 public class ListNode {
 3     int val;
 4     ListNode next = null;
 5 
 6     ListNode(int val) {
 7         this.val = val;
 8     }
 9 }*/
10 public class Solution {
11    
12     public ListNode ReverseList(ListNode head) {
13         ListNode lastNode = null, p = head, nextNode;
14         if (head == null) return null;
15         
16         for (;p.next != null; p = nextNode) {
17             nextNode = p.next;
18             p.next = lastNode;
19             lastNode = p;
20             
21         }
22         p.next = lastNode;
23         return p;
24     }
25 }