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廣度優(yōu)先遍歷豌鸡，建一個隊(duì)列炭剪，每次壓入左右子節(jié)點(diǎn)每币，知道隊(duì)列為空。
代碼：
# -*- coding:utf-8 -*-
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
# 返回從上到下每個節(jié)點(diǎn)值列表嗡害，例：[1,2,3]
def PrintFromTopToBottom(self, root):
# write code here
self.st = [root]
self.ans = []
if root == None:
return self.ans
while self.st != None:
if len(self.st) == 0:
break
p = self.st[0]
del self.st[0]
if p.left:
self.st.append(p.left)
if p.right:
self.st.append(p.right)
self.ans.append(p.val)
return self.ans
