I used a recursive solution to swap the nodes. This can also be solved by using or .
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
if root is None:
return
root.left, root.right = root.right, root.left
self.invertTree(root.left)
self.invertTree(root.right)
return root