LeetCode 226 - 翻转二叉树

class Solution:
    def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]:
        if root is None:
            return None
        tempNode = root.left
        root.left = root.right
        root.right = tempNode
        self.invertTree(root.left)
        self.invertTree(root.right)
        return root