public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
        List<List<Integer>> resultList = new ArrayList<List<Integer>>();
        if (root == null) return resultList ;
        Queue<TreeNode> quene = new LinkedList<TreeNode>();

        int sign = 1; //1代表从左到右，-1代表从右到左
        int depSum = 1;
        quene.add(root); //加入首节点
        while (quene.size()!=0){
            LinkedList<Integer> tempList = new LinkedList<Integer>();
            //临时存储，用于队列循环
            int temp = depSum;
            //重置次数
            depSum = 0;
            while (temp>0){
                //取出元素加入
                TreeNode node = quene.poll();
                if (node.left != null) {
                    quene.add(node.left);
                    depSum++;
                }
                if (node.right != null){
                    quene.add(node.right);
                    depSum++;
                } 
                if (sign == 1) tempList.addLast(node.val);
                else if (sign == -1) tempList.addFirst(node.val);
                temp --;
            }
            sign = -sign;
            resultList.add(tempList);
        }
        return resultList;
    }