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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] ]
class Solution(object): def levelOrderBottom(self, root): if not root: return [] stack, ans = [root], [] while stack: temp, stack_new = [], [] for x in stack: temp.append(x.val) if x.left: stack_new.append(x.left) if x.right: stack_new.append(x.right) ans = [temp] + ans stack = stack_new return ans
Leetcode 107 Binary Tree Level Order Traversal II
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原文地址：http://www.cnblogs.com/lilixu/p/5550395.html
