题目描述

请实现一个函数按照之字形打印二叉树，即第一行按照从左到右的顺序打印，第二层按照从右至左的顺序打印，第三行按照从左到右的顺序打印，其他行以此类推。

 1 # -*- coding:utf-8 -*-
 2 # class TreeNode:
 3 #     def __init__(self, x):
 4 #         self.val = x
 5 #         self.left = None
 6 #         self.right = None
 7 class Solution:
 8     def Print(self, pRoot):
 9         # write code here
10         if pRoot == None:
11             return []
12         stack1=[pRoot]
13         stack2=[]
14         ret=[]
15         while stack1 or stack2:
16             if stack1:
17                 tmpRet = []
18                 while stack1:
19                     tmpNode = stack1.pop()
20                     tmpRet.append(tmpNode.val)
21                     if tmpNode.left:
22                         stack2.append(tmpNode.left)
23                     if tmpNode.right:
24                         stack2.append(tmpNode.right)
25                 ret.append(tmpRet)
26             if stack2:
27                 tmpRet=[]
28                 while stack2:
29                     tmpNode = stack2.pop()
30                     tmpRet.append(tmpNode.val)
31                     if tmpNode.right:
32                         stack1.append(tmpNode.right)
33                     if tmpNode.left:
34                         stack1.append(tmpNode.left)
35                 ret.append(tmpRet)
36         return ret

2020-01-01 17:39:12