leetcodeday226–翻转二叉树

给你一棵二叉树的根节点 root ，翻转这棵二叉树，并返回其根节点。

示例 1：

输入：root = [4,2,7,1,3,6,9]
输出：[4,7,2,9,6,3,1]

# [226] 翻转二叉树
#

# @lc code=start
# 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:
        
        def traversal(root: TreeNode):
            if root == None:
                return
            rev=root.left
            root.left=root.right
            root.right=rev
            traversal(root.left)    # 左
            traversal(root.right)   # 右

        traversal(root)
        return root
# @lc code=end