題目鏈接

https://leetcode.com/problems/binary-tree-level-order-traversal-ii/

題目原文

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},

return its bottom-up level order traversal as:

題目大意

自下而上層次遍歷二叉樹

解題思路

用之前層次遍歷二叉樹的算法，最后翻轉一下

代碼

# Definition for a binary tree node. # class TreeNode(object): # def __init__(self, x): # self.val = x # self.left = None # self.right = Noneclass Solution(object):def help(self, root, level, ans):if root:if len(ans) < level + 1:ans.append([])ans[level].append(root.val)self.help(root.left, level + 1, ans)self.help(root.right, level + 1, ans)def levelOrderBottom(self, root):""":type root: TreeNode:rtype: List[List[int]]"""ans = []self.help(root, 0, ans)ans.reverse()return ans

轉載于:https://www.cnblogs.com/slurm/p/5262659.html

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