思路

采用先序遍歷，可以通過新建根節點node，將原來root的右子樹連到去node的左子樹中，root的左子樹連到去node的右子樹中。

# 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: Optional[TreeNode]) -> Optional[TreeNode]:#先序遍歷,遍歷整顆樹def inverse(node):if node==None:return Noneroot=TreeNode(node.val)root.left=inverse(node.right)root.right=inverse(node.left)return rootreturn inverse(root)