【剑指Offer】22.从上往下打印二叉树（Python实现）

题目描述

从上往下打印出二叉树的每个节点，同层节点从左至右打印。

解法一：优先级队列

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    # 返回从上到下每个节点值列表，例：[1,2,3]
    def PrintFromTopToBottom(self, root):
        queue = []
        result = []
        if root == None:
            return result
        queue.append(root)
        while queue:
            newNode = queue.pop(0)
            result.append(newNode.val)
            if newNode.left != None:
                queue.append(newNode.left)
            if newNode.right != None:
                queue.append(newNode.right)
        return result