Question

I’m trying to figure out how to create a binary tree class in Managed C++ for a school project. I’ve found really good examples in unmanaged C++ and some in C#, so I have been able to get a fairly good understanding ow what’s going on, but I just can’t seem to figure it out in Managed C++. What I’d like to find out is: why am I getting the stack overflow (see below), and is this a wise approach? Here’s my class:

#pragma once

#include "stdafx.h"
#include <iostream>
#include <deque>
#include <climits>

using namespace std;
using namespace System;
using namespace System::Collections;

ref struct Node
{
int data;
Node ^parent;
Node ^left;
Node ^right;

// constructors
// default constructor

Node (){}
// constructor that takes a node with no leafs
// a constructor that accepts a new node with no children
Node(int input)
{
    Node ^node = gcnew Node(input);
    node->data =input;
    node->left = nullptr;
    node->right = nullptr;
    node->parent = nullptr;
}

// method to create a new Node 
Node ^newNode(int data)
{
    Node ^node = gcnew Node;
    node->data = data;
    node->left = nullptr;
    node->right = nullptr;
    node->parent = nullptr;

    return node;
}

// method that inserts a new node into an existing tree
Node ^insertNode(Node ^node, int input)
{
    Node ^p;
    Node ^returnNode;
    if (node == nullptr)
    {
        returnNode = newNode(input);
        returnNode->parent = p;
        return returnNode;
    }

    if (input <= node->data)
    {
        p = node;
        node->left = insertNode(node->left, input);
    }

    else
    {
        p = node;
        node->right = insertNode(node->right, input);
    }
    return node;
}

};

And when I create a new instance, and try to add a node, I get a stack overflow exception.

#include "stdafx.h"
#include "GenericNodeClass.h"
#include "BinarySearchTreeClass.h"

using namespace std;
using namespace System;

int main ()
{
BinarySearchTreeClass^ BTree = gcnew BinarySearchTreeClass();

Node ^newNode = gcnew Node(7);
newNode = newNode->insertNode(newNode, 6);  // this just looks stupid
return 0;
}

Answer 1

In your Node constructor…

Node(int input)
{

…you unconditionally call the Node constructor…

    Node ^node = gcnew Node(input);

That can’t end well. Why are you constructing a new Node in the Node constructor? When the Node constructor is called, it is called to construct the *this object–instead of creating a new Node, you should initialize the current instance.

Likewise in your insertNode member function–it already has access to the *this object; there’s no need to pass it via a separate parameter.