3、从尾到头打印列表
参考答案：
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> result = new ArrayList();
while(!stack.isEmpty()){
result.add(stack.pop());
}
return result;
}
}