226. 翻转二叉树

题目链接：https://leetcode.cn/problems/invert-binary-tree/
难度：简单

描述：
给你一棵二叉树的根节点 root ，翻转这棵二叉树，并返回其根节点。

题解

# 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: TreeNode) -> TreeNode:
        def recursion(root):
            if root is None:
                return
            left = recursion(root.left)
            right = recursion(root.right)
            root.left, root.right = right, left
            return root
        return recursion(root)