leetCode-226:Invert Binary Tree

问题描述

给定一个二叉树，要求将二叉树进行反转。题目链接：点我

样例输入输出

输入：root = [4,2,7,1,3,6,9]

输出：[4,7,2,9,6,3,1]

解释：

输入：root = [1]

输出：1

问题解法

使用递归将二叉树反转，代码如下

/**
 * 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.left);
        TreeNode right = invertTree(root.right);
        root.left = right;
        root.right = left;
        return root;
    }
}