# 226. Invert Binary Tree

#### Easy

***

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`

```python
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
        if root is None:
            return root
        self.invertTree(root.left)
        self.invertTree(root.right)
        root.left, root.right = root.right, root.left
        return root
```