invert_binary_tree 

 1from typing import Optional
 2from utils import TreeNode
 3
 4
 5# @leet start
 6class Solution:
 7    def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
 8        """
 9        To invert a binary tree, we want to change every left and right subtree.
10        To do this, we swap them and then iterate through the left and right sutbrees of the root.
11        This is easiest done recursively.
12        """
13        if not root:
14            return
15        root.left, root.right = root.right, root.left
16        self.invertTree(root.left)
17        self.invertTree(root.right)
18        return root
19
20
21# @leet end
22
23
24def test():
25    assert 2 + 2 == 4
class Solution: 
 7class Solution:
 8    def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
 9        """
10        To invert a binary tree, we want to change every left and right subtree.
11        To do this, we swap them and then iterate through the left and right sutbrees of the root.
12        This is easiest done recursively.
13        """
14        if not root:
15            return
16        root.left, root.right = root.right, root.left
17        self.invertTree(root.left)
18        self.invertTree(root.right)
19        return root
def invertTree(self, root: Optional[utils.TreeNode]) -> Optional[utils.TreeNode]: 
 8    def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
 9        """
10        To invert a binary tree, we want to change every left and right subtree.
11        To do this, we swap them and then iterate through the left and right sutbrees of the root.
12        This is easiest done recursively.
13        """
14        if not root:
15            return
16        root.left, root.right = root.right, root.left
17        self.invertTree(root.left)
18        self.invertTree(root.right)
19        return root

To invert a binary tree, we want to change every left and right subtree. To do this, we swap them and then iterate through the left and right sutbrees of the root. This is easiest done recursively.

def test(): 
25def test():
26    assert 2 + 2 == 4