// * Definition for a binary tree node. // https://leetcode.com/problems/invert-binary-tree/description/ 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; } } public class invertBinaryTree { public TreeNode invertTree(TreeNode root) { if (root == null) return null; TreeNode temp = root.left; root.left = root.right; root.right = temp; invertTree(root.left); invertTree(root.right); return root; } public static void main(String[] args) { // Create the input binary tree: [4,2,7,1,3,6,9] TreeNode root = new TreeNode(4); root.left = new TreeNode(2); root.right = new TreeNode(7); root.left.left = new TreeNode(1); root.left.right = new TreeNode(3); root.right.left = new TreeNode(6); root.right.right = new TreeNode(9); // Print the original tree System.out.println("Original tree:"); printTree(root); // Invert the tree invertBinaryTree solution = new invertBinaryTree(); TreeNode invertedRoot = solution.invertTree(root); // Print the inverted tree System.out.println("\nInverted tree:"); printTree(invertedRoot); } // Helper method to print the tree (in-order traversal) private static void printTree(TreeNode root) { if (root == null) return; printTree(root.left); System.out.print(root.val + " "); printTree(root.right); } }