Sum of leaf node in BST using recursion in c++

C++ program for Sum of leaf node in BST using recursion. Here mentioned other language solution.

// Include header file
#include <iostream>
using namespace std;
// C++ program for
// Sum of all leaf nodes of binary search tree
// Using recusion
class TreeNode
{
	public: int data;
	TreeNode *left;
	TreeNode *right;
	TreeNode(int data)
	{
		this->data = data;
		this->left = nullptr;
		this->right = nullptr;
	}
};
class BinarySearchTree
{
	public: TreeNode *root;
	BinarySearchTree()
	{
		this->root = nullptr;
	}
	// insert a new node
	void addNode(int data)
	{
		// Create a new node
		TreeNode *node = new TreeNode(data);
		if (this->root == nullptr)
		{
			// When adds a first node in bst
			this->root = node;
		}
		else
		{
			TreeNode *find = this->root;
			// Add new node to proper position
			while (find != nullptr)
			{
				if (find->data >= data)
				{
					if (find->left == nullptr)
					{
						// When left child empty
						// So add new node here
						find->left = node;
						return;
					}
					else
					{
						// Otherwise
						// Visit left sub-tree
						find = find->left;
					}
				}
				else
				{
					if (find->right == nullptr)
					{
						// When right child empty
						// So add new node here
						find->right = node;
						return;
					}
					else
					{
						// Visit right sub-tree
						find = find->right;
					}
				}
			}
		}
	}
	// Sum of leaf nodes
	int leafNodeSum(TreeNode *node)
	{
		if (node != nullptr)
		{
			if (node->left == nullptr && node->right == nullptr)
			{
				// When node is leaf node
				return node->data;
			}
			// Visit to left and right subtree
			return this->leafNodeSum(node->left) + 
              		this->leafNodeSum(node->right);
		}
		return 0;
	}
};
int main()
{
	BinarySearchTree *tree = new BinarySearchTree();
	// Add nodes in binary search tree
	/*
	            5
	          /   \ 
	         /     \
	        3       9
	       / \     /  \
	      2   4   8    10
	             / 
	            6

	*/
	tree->addNode(5);
	tree->addNode(3);
	tree->addNode(9);
	tree->addNode(2);
	tree->addNode(4);
	tree->addNode(8);
	tree->addNode(10);
	tree->addNode(6);
	// Test
	cout << tree->leafNodeSum(tree->root);
	return 0;
}

Output

22