题目

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]

解

class Solution {public TreeNode invertTree(TreeNode root) {dfs(root);return root;}public TreeNode dfs(TreeNode root) {if (root == null) {return root;}TreeNode left = dfs(root.left);TreeNode right = dfs(root.right);root.right = left;root.left = right;return root;}
}