# LeetCode 226: Invert Binary Tree — Step-by-Step Visual Trace

**Easy** — Binary Tree | Recursion | Depth-First Search | Tree Traversal

## The Problem

Given the root of a binary tree, invert the tree by swapping the left and right children of every node, and return the root of the inverted tree.

## Approach

Use a recursive depth-first approach to traverse the tree. At each node, swap the left and right children, then recursively invert both subtrees. The base case returns None for null nodes.

**Time:** O(n) · **Space:** O(h)

## Code

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

        # Swap left and right subtrees
        root.left, root.right = root.right, root.left

        # Recursively invert left and right subtrees
        self.invertTree(root.left)
        self.invertTree(root.right)

        return root
```

## Watch It Run

> **[Open interactive visualization](https://tracelit.dev/app?trace=0226_invert-binary-tree)**

> **Try it yourself:** Open [TraceLit](https://tracelit.dev/app?trace=0226_invert-binary-tree) and step through every line.

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