《剑指Offer》刷题笔记——面试题32 II. 从上到下打印二叉树II

难度:简单 一、题目描述: 二、解题分析: # Definition for a binary tree node. # class TreeNode: # def __init__(self, x): # self.val = x # self.left = None # self.right = None class Solution: def levelOrder(self, root: TreeNode) -> List[List[int]]: if not root: return []