https://leetcode.cn/problems/invert-binary-tree/
需要注意的点

  1. 递归到子节点， 从子节点开始翻转

  2. 翻转节点左右节点，递归处理左节点，然后递归右节点

    1. # Definition for a binary tree node.
    2. # class TreeNode:
    3. #     def __init__(self, val=0, left=None, right=None):
    4. #         self.val = val
    5. #         self.left = left
    6. #         self.right = right
    7. class Solution:
    8.  def invertTree(self, root: TreeNode) -> TreeNode:
    10.      if  not root:
    11.          return root
    13.      left  = self.invertTree(root.left)
    14.      right = self.invertTree(root.right)
    16.      root.left = right
    17.      root.right = left
    19.      return root

    ```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:

  1.     def traverse(node: TreeNode) -> TreeNode:
  3.         if not node:
  4.             return 
  6.         tmp = node.right
  7.         node.right = node.left
  8.         node.left = tmp
  10.         traverse(node.left)
  11.         traverse(node.right)
  13.     traverse(root)
  14.     return root

```