# 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