目录

226. 翻转二叉树

思路

代码 

本地代码测试

---

不管前方的路有多苦

只要走的方向正确

不管多么崎岖不平

都比站在原地更接近幸福

                        —— 24.10.21 

226. 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]

示例 2：

输入：root = [2,1,3]
输出：[2,3,1]

示例 3：

输入：root = []
输出：[]

思路

代码 

/**
 * 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 static TreeNode invertTree(TreeNode root) {
        fn(root);
        return root;
    }

    private static void fn(TreeNode root) {
        if (root == null) {
            return;
        }
        TreeNode temp = root.left;
        root.left = root.right;
        root.right = temp;

        fn(root.left);
        fn(root.right);
    }
}

本地代码测试

public class LeetCode226ReverseBinaryTree {
    public static TreeNode invertTree(TreeNode root) {
        fn(root);
        return root;
    }

    private static void fn(TreeNode root) {
        if (root == null) {
            return;
        }
        TreeNode temp = root.left;
        root.left = root.right;
        root.right = temp;

        fn(root.left);
        fn(root.right);
    }

    private static void Print(TreeNode root, String indent) {
        if (root == null) {
            return;
        }
        System.out.println(indent + root.value);
        Print(root.left, indent + "  |-- ");
        Print(root.right, indent + "  |-- ");
    }

    public static void main(String[] args) {
        TreeNode root = new TreeNode(1,
                new TreeNode(2,
                        new TreeNode(4),
                        new TreeNode(5,
                                new TreeNode(7), null)),
                new TreeNode(3,
                        null,
                        new TreeNode(6)));
        TreeNode invertedRoot = invertTree(root);
        Print(invertedRoot,"");

    }
}