思路

使用递归实现

出口 ，遇到null

每一层要做：把下层放进去，把本层放下去

代码

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
  class Solution {

        public ListNode result=new ListNode(0);
        public ListNode resultCur=result;


        public ListNode trainningPlan(ListNode head) {
             if (head == null) {
                return null;
            }
            ListNode digui = digui(head, head);
            return digui;
        }
        public ListNode digui(ListNode realHead,ListNode head){
            if (head == null) {
                return result;
            }
            //将后面的放入
            digui(realHead,head.next);
            //将这个本身放入
            resultCur.val = head.val;
            if (head != realHead) {
                //然后resultCur向后走
                ListNode listNode = new ListNode();
                resultCur.next = listNode;
            }
            resultCur = resultCur.next;
            return result;
        }

    }

记录

总结