链表反转递归解法

递归思路

如果要实现节点1及节点2的指针反转

head.next.next = head;
head.next = null; 

递归代码如下：

package com.aliyun.etmp.datastructure;

public class ListNode {

    private int val;

    private ListNode next;

    private ListNode (int val, ListNode next) {
        this.val = val;
        this.next = next;
    }

    private static ListNode buildListNode() {
        ListNode node5 = new ListNode(5,  null);
        ListNode node4 = new ListNode(4,  node5);
        ListNode node3 =