题目

我的代码（递归）

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def invertTree(self, root: TreeNode) -> TreeNode:
        if root:
            self.invertTree(root.left)
            self.invertTree(root.right)
            tmp=root.right
            root.right=root.left
            root.left=tmp
            return root

高效方法：

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