0226_invert_binary_tree.py

"""
neetcode - trees - 1

sol:
reverse current node's left and right
recurse on left and right
recursion ends at None
"""

from __future__ import annotations


class TreeNode:
    def __init__(
        self, val: int = 0, left: TreeNode | None = None, right: TreeNode | None = None
    ):
        self.val = val
        self.left = left
        self.right = right


class Solution:
    def invertTree(self, root: TreeNode | None) -> TreeNode | None:
        if root:
            root.left, root.right = root.right, root.left
            self.invertTree(root.left)
            self.invertTree(root.right)
        return root