1161.Maximum Level Sum of a Binary Tree
===

###### tags: `Medium`,`Tree`,`DFS`,`BFS`,`Binary Tree`

[1161. Maximum Level Sum of a Binary Tree](https://leetcode.com/problems/minimum-absolute-difference-in-bst/)

### 題目描述

Given the `root` of a binary tree, the level of its root is `1`, the level of its children is `2`, and so on.
Return the smallest level `x` such that the sum of all the values of nodes at level `x` is maximal.

### 範例

**Example 1:**


Input: root = [1,7,0,7,-8,null,null]
Output: 2
Explanation: 
Level 1 sum = 1.
Level 2 sum = 7 + 0 = 7.
Level 3 sum = 7 + -8 = -1.
So we return the level with the maximum sum which is level 2.

**Example 2:**

Input: root = [989,null,10250,98693,-89388,null,null,null,-32127]
Output: 2

**Constraints**:

* The number of nodes in the tree is in the range [1, 10^4^].
* -10⁵ <= `Node.val` <= 10⁵

### 解答

### Reference

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