牛课力扣

该二叉树之字形层序遍历的结果是
[
[1],
[3,2],
[4,5]
]

# -*- coding:utf-8 -*-
# class TreeNode:
# def __init__(self, x):
# self.val x
# self.left None
# self.right None
class Solution:
 def Print(self, pRoot):
 # write code here
 if not pRoot:
 return []
 queue [pRoot]
 res []
 flag 0
 while len(queue) 0:
 if flag%2 0: #对层进行判断 偶数层保持不变 奇数层进行翻转。
 res.append([node.val for node in queue])
 else:
 res.append([node.val for node in reversed(queue)])
 lay []
 for node in queue:
 if node.left:
 lay.append(node.left)
 if node.right:
 lay.append(node.right)
 queue lay
 flag 1
 return res