思路

采用先序遍历，可以通过新建根节点node，将原来root的右子树连到去node的左子树中，root的左子树连到去node的右子树中。

# 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]:#先序遍历,遍历整颗树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)