原题地址：http://oj.leetcode.com/problems/binary-tree-zigzag-level-order-traversal/
题意：
Given a binary tree, return the zigzag level order traversal of its nodes‘ values. (ie, from left to right, then right to left for the next level and alternate between).
For example:
Given binary tree {3,9,20,#,#,15,7},
3
/ 9 20
/ 15 7
return its zigzag level order traversal as:
[ [3], [20,9], [15,7] ]
confused
what "{1,#,2,3}" means? >
read more on how binary tree is serialized on OJ.
OJ‘s Binary Tree Serialization:
The serialization of a binary tree follows a level order traversal, where ‘#‘ signifies a path terminator where no node exists below.
Here‘s an example:
1
/ 2 3
/
4
5
The above binary tree is
serialized as "{1,2,3,#,#,4,#,#,5}".解题思路：这道题和层序遍历那道题差不多，区别只是在于奇数层的节点要翻转过来存入数组。http://www.cnblogs.com/zuoyuan/p/3722004.html
代码：
# Definition for a binary tree node # class TreeNode: # def __init__(self, x): # self.val = x # self.left = None # self.right = None class Solution: # @param root, a tree node # @return a list of lists of integers def preorder(self, root, level, res): if root: if len(res) < level+1: res.append([]) if level % 2 == 0: res[level].append(root.val) else: res[level].insert(0, root.val) self.preorder(root.left, level+1, res) self.preorder(root.right, level+1, res) def zigzagLevelOrder(self, root): res=[] self.preorder(root, 0, res) return res
[leetcode]Binary Tree Zigzag Level Order Traversal @ Python,布布扣,bubuko.com