# Invert Binary Tree

## Problem

Given the root of a binary tree, invert the tree, and return its root.

Example 1:

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

Example 2:

```
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

## Solution

I’ve studied extensively for this because of that Homebrew incident! This is literally in my Anki deck.

```
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public TreeNode invertTree(TreeNode root) {
if (root == null) {
return root;
}
var tmp = root.left;
root.left = invertTree(root.right);
root.right = invertTree(tmp);
return root;
}
}
```