226. Invert Binary Tree-翻转二叉树

Invert a binary tree.

Example:

Input:

Output:

Solution in python:

# 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:
        if not root:
            return None
        else:
            root.left, root.right = self.invertTree(root.right), self.invertTree(root.left)
        return root