Class to invert a binary tree

InvertBinaryTree.java

/* File:    InvertBinaryNode.java
 * Created: 8/30/2018
 * Author:  Sabbir Manandhar
 *
 * Copyright (c) 2018 Hogwart Inc.
 */

//=======================================================================================

import java.util.Stack;

/**
 * Class to invert a Binary Tree.
 * Inversion of a binary tree means to invert all the left and right node. That is
 * make left child right and right child left.
 *
 * @author Sabbir Manandhar
 *         manandharsabbir@gmail.com
 * @version 1.0
 */
public class InvertBinaryTree {

  /**
   * This is a recursive method to invert the tree.
   * @param root root of the tree to invert
   * @return root of inverted tree
   */
  public TreeNode invertTree(TreeNode root) {
    if (root == null) return root;

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

  //-------------------------------------------------------------------------------------

  /**
   * This is iterative method to invert the tree
   * @param root root of the tree to invert
   * @return root of inverted tree
   */
  public TreeNode invertTreeIterative(TreeNode root) {
    if (root == null) return root;

    Stack<TreeNode> stack = new Stack<>();
    stack.push(root);

    while (!stack.isEmpty()) {
      TreeNode node = stack.pop();
      if (node.left != null) {
        stack.push(node.left);
      }
      if (node.right != null) {
        stack.push(node.right);
      }

      TreeNode temp = node.left;
      node.left = node.right;
      node.right = temp;
    }
    return root;
  }

} // InvertBinaryTree

//=======================================================================================

class TreeNode {
  int val;
  TreeNode left;
  TreeNode right;

  /**
   * Constructor
   * @param val
   */
  public TreeNode(int val) {
    this.val = val;
  } // TreeNode

} // TreeNode