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# 1161. Maximum Level Sum of a Binary Tree

<https://leetcode.com/problems/maximum-level-sum-of-a-binary-tree>

## Description

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**.

**Example 1:**

![](https://assets.leetcode.com/uploads/2019/05/03/capture.JPG)

```
**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, 104]`.
* `-105 <= Node.val <= 105`

## ac

```java
```