"""

Invert Binary Tree

Inverts a binary tree by swapping the left and right children of every node.

Reference: https://en.wikipedia.org/wiki/Binary_tree

Complexity:

Time: O(n)

Space: O(n) due to recursion stack

"""

from __future__ import annotations

from algorithms.tree.tree import TreeNode

def reverse(root: TreeNode | None) -> None:

"""Invert a binary tree in-place by swapping left and right children.

Args:

root: The root of the binary tree to invert.

Examples:

>>> reverse(None)

"""

if root is None:

return

root.left, root.right = root.right, root.left

if root.left:

reverse(root.left)

if root.right:

reverse(root.right)