Python：把二叉樹打印成多行

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題目描述

從上到下按層打印二叉樹，同一層結點從左至右輸出。每一層輸出一行。

# -*- coding:utf-8 -*-
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None
class Solution:
    # 返回二維列表[[1,2],[4,5]]
    def Print(self, pRoot):
        # write code here
        if not pRoot:
            return []
        res, tree = [], [pRoot]
        while tree:
            row, sub_tree = [], []
            for item in tree:
                row.append(item.val)
                if item.left:
                    sub_tree.append(item.left)
                if item.right:
                    sub_tree.append(item.right)
            res.append(row)
            tree = sub_tree
        return res