# 0226. Invert Binary Tree

https://leetcode.com/problems/invert-binary-tree

## Description

Given the `root` of a binary tree, invert the tree, and return _its root_.

**Example 1:**

![](https://assets.leetcode.com/uploads/2021/03/14/invert1-tree.jpg)

```
**Input:** root = [4,2,7,1,3,6,9]
**Output:** [4,7,2,9,6,3,1]
```

**Example 2:**

![](https://assets.leetcode.com/uploads/2021/03/14/invert2-tree.jpg)

```
**Input:** root = [2,1,3]
**Output:** [2,3,1]
```

**Example 3:**

```
**Input:** root = []
**Output:** []
```

**Constraints:**

* The number of nodes in the tree is in the range `[0, 100]`.
* `-100 <= Node.val <= 100`

## ac

```java
```
