再来一道

思路一：递归

/**
*    public class ListNode {
*        int val;
*        ListNode next = null;
*
*        ListNode(int val) {
*            this.val = val;
*        }
*    }
*
*/
//递归算法
import java.util.ArrayList;
public class Solution {
    ArrayList<Integer> list = new ArrayList<Integer>();
    public ArrayList<Integer> printListFromTailToHead(ListNode listNode) {
        if(listNode==null){
            return list;
        }
        printListFromTailToHead(listNode.next);
        list.add(listNode.val);
        return list;
    }
}

思路二：借助栈的先进后出特性
1、遍历链表，元素值正序入栈
2、逆序出栈到ArrayList

import java.util.*;
/**
*    public class ListNode {
*        int val;
*        ListNode next = null;
*
*        ListNode(int val) {
*            this.val = val;
*        }
*    }
*
*/
import java.util.ArrayList;
public class Solution {
    public ArrayList<Integer> printListFromTailToHead(ListNode listNode) {
         ArrayList<Integer> list = new ArrayList<Integer>();

        if(listNode==null){
            return list;
        }
        Stack<Integer> stack = new Stack<>();
        while(listNode!=null){
            stack.push(listNode.val);
            listNode = listNode.next;
        }

        while(!stack.isEmpty()){
            list.add(stack.pop());
        }
        return list;
    }
}