【剑指offer】从尾到头打印链表

0.递归写法

public class Solution {
    ArrayList list = new ArrayList();
    public ArrayList printListFromTailToHead(ListNode listNode) {
        if(listNode!=null){
            printListFromTailToHead(listNode.next);
            list.add(listNode.val);
        }
        return list;
    }
}

1.栈的简单运用

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

2.调了一个函数

public class Solution {
    public ArrayList printListFromTailToHead(ListNode listNode) {
        ArrayList list = new ArrayList();
        while (listNode != null) {
            list.add(0, listNode.val);
            listNode = listNode.next;
        }
        return list;
    }
}