# Leetcode 226 Invert Binary Tree.

As I have already build this blog, I will move my notes of Leetcode problem from my Evernote. But it would take time.

**Problem 226 Invert Binary Tree**

Invert a binary tree.

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

to

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

Trivia:

This problem was inspired by this original tweet by Max Howell:

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

The problem here is not so difficult comparing to another Problem, which has the title of *Populating Next Right Pointers in Each Node*.

Just use the recursive to change every node's left and right child node. Then it is done.

And if you do not want to use recursive, then, use a stack to deal with it.

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