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# Invert Binary Tree

## [Invert Binary Tree](https://leetcode.com/problems/invert-binary-tree)

Invert a binary tree.

**Example:**

Input:

```

     4
   /   \
  2     7
 / \   / \
1   3 6   9
```

Output:

```

     4
   /   \
  7     2
 / \   / \
9   6 3   1
```

**Trivia:**\
 This problem was inspired by [this original tweet](https://twitter.com/mxcl/status/608682016205344768) by [Max Howell](https://twitter.com/mxcl):

> Google: 90% of our engineers use the software you wrote (Homebrew), but you can’t invert a binary tree on a whiteboard so f\*\*\* off.

## Solutions

### 🧠 Cpp

```cpp
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* invertTree(TreeNode* root)
    {
        if(!root) return nullptr;
        std::swap(root->left, root->right);
        invertTree(root->left);
        invertTree(root->right);
        return root;
    }
};
```