原题地址：http://oj.leetcode.com/problems/binary-tree-level-order-traversal-ii/
题意：
Given a binary tree, return the bottom-up level order traversal of its nodes‘ values. (ie, from left to right, level by level from leaf to root).
For example:
Given binary tree {3,9,20,#,#,15,7},
3
/ 9 20
/ 15 7
return its bottom-up level order traversal as:
[ [15,7] [9,20], [3], ]
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：由于编程语言为python，所以其实在Binary Tree Level Order
Traversal这道题（http://www.cnblogs.com/zuoyuan/p/3722004.html）的基础上加一句res.reverse()就可以了。
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([]) res[level].append(root.val) self.preorder(root.left, level+1, res) self.preorder(root.right, level+1, res) def levelOrderBottom(self, root): res=[] self.preorder(root, 0, res) res.reverse() return res
[leetcode]Binary Tree Level Order Traversal II @ Python,布布扣,bubuko.com