Leetcode226. 翻转二叉树(Java)

1.问题描述

翻转一棵二叉树。

示例：

输入：

     4
   /   \
  2     7
 / \   / \
1   3 6   9
输出：

     4
   /   \
  7     2
 / \   / \
9   6 3   1

力扣（LeetCode）;

2.方案

递归的方式解决。

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode invertTree(TreeNode root) {
        if(root == null) return root;
        TreeNode invertTree = new TreeNode(0);

        invertTree.val = root.val;
        invertTree.left = invertTree(root.right);
        invertTree.right = invertTree(root.left);

        return invertTree;
    }
}