# Invert Binary Tree

Iterative:

```python
class Solution:
    def invertTree(self, root: TreeNode) -> TreeNode:
        if not root:
            return None
        queue = []
        queue.append(root)
        while queue:
            curr = queue.pop()
            left = curr.left
            curr.left = curr.right
            curr.right = left
            if curr.left:
                queue.append(curr.left)
            if curr.right:
                queue.append(curr.right)
        return root
        
```

Recursive

```python
class Solution:
    def invertTree(self, root: TreeNode) -> TreeNode:
        if not root:
            return None
        left = self.invertTree(root.left)
        right = self.invertTree(root.right)
        root.left = right
        root.right = left
        return root
```