# Definition for a binary tree node.

# class TreeNode(object):

#     def __init__(self, x):

#         self.val = x

#         self.left = None

#         self.right = None

class Solution(object):

    def levelOrder(self, root):

        """

        :type root: TreeNode

        :rtype: List[List[int]]

        """

        res=[]

        if root is None:

            return res

        level=0

        rs=self.levelOrderRe(root,level,res)

        return rs

    def levelOrderRe(self,tree,level,res):

        if tree is None:

            return res

        if len(res) < level+1:

            res.append([])

        res[level].append(tree.val)

        res=self.levelOrderRe(tree.left,level+1,res)

        res=self.levelOrderRe(tree.right,level+1,res)

        return res