226. 翻转二叉树

难度：简单

题目描述：

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]
示例 2：

输入：root = [2,1,3]
输出：[2,3,1]
示例 3：

输入：root = []
输出：[]

解题思路：递归

Java程序：

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode invertTree(TreeNode root) {
        if(root == null){
            return root;
        }
        TreeNode left = invertTree(root.right);
        TreeNode right = invertTree(root.left);
        root.right = right;
        root.left = left;
        return root;
    }
}

标签：right,TreeNode,val,示例,二叉树,226,left,root,翻转
来源： https://blog.csdn.net/LIsaWinLee/article/details/123635846