3.从头到尾打印链表

import java.util.Stack;
import java.util.ArrayList;

public class Solution {

    public ArrayList<Integer> printListFromTailToHead(ListNode listNode) {
        Stack<Integer> stack = new Stack<>();
        while (listNode != null){
            stack.push(listNode.val);
            listNode = listNode.next;
        }
        ArrayList<Integer> list = new ArrayList<>();
        while(!stack.empty()){
            list.add(stack.pop());
        }
        return list;
    }
}