Binary search tree not printing

[saherch]

Hello,
I am trying to print a binary search tree. By debugging i know that root remains equal to 'nullptr' every time it enters the function.

void BSTree::AddNode(int a, Node * ptr )

Thus nothing is printed ny print function aswell. Can some body help me with fixing this code? Would be of great help.

Regards
Saherch

#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>
using namespace std;

class Node
{
private:
    int data;
    Node * left;
    Node * right;

public:
    Node();
    void SetData(int);
    int getData();
    void Setleft(Node *);
    Node * getleft();
    void Setright(Node *);
    Node * getright();
};

Node::Node()
{
    data = 0;
    left = nullptr;
    right = nullptr;
}

void Node::SetData(int a)
{
    data = a;
}

int Node::getData()
{
    return data;
}

void Node::Setleft(Node * ptr)
{
    left = ptr;
}

Node * Node::getleft()
{
    return left;
}

void Node::Setright(Node * ptr)
{
    right = ptr;
}


Node * Node::getright()
{
    return right;
}


class BSTree
{
private:
    Node * root;

public:
    BSTree();
    void setRoot(Node *);
    Node * getRoot();
    void AddNode(int, Node *);
    void print(Node *);
};

BSTree::BSTree()
{
    root = nullptr;
}

void BSTree::setRoot(Node * p)
{
    root = p;
}

Node * BSTree::getRoot()
{
    return root;
}

void BSTree::AddNode(int a, Node * ptr )
{
    if (ptr == nullptr)
    {
        Node * temp = new Node();
        temp->SetData(a);
        temp->Setleft(nullptr);
        temp->Setright(nullptr);
        ptr = temp;

    }
    else
    {
        if (a < ptr->getData())
        {
            AddNode(a, ptr->getleft());
        }
        else if (a> ptr->getData())
        {
            AddNode(a, ptr->getright());
        }
    }
}

void BSTree::print(Node * n)
{
    cout<<n->getData()<<", ";
    print(n->getleft());
    print(n->getright());
}


int main(int argc, char *argv[])
{
    BSTree tree;

    tree.AddNode(5,tree.getRoot());
    tree.AddNode(2,tree.getRoot());
    tree.AddNode(10,tree.getRoot());

    tree.print(tree.getRoot());

    return 0;
}

[ne555]

> void BSTree::AddNode(int a, Node * ptr )
pass a copy of the pointer.

> ptr = temp;
modifies the copy of the pointer.

> tree.AddNode(10,tree.getRoot());
that looks cumbersome
tree.Add(10);


> #include <opencv2/core/core.hpp>
completely unrelated.
Try to create a minimal example.

[saherch]

1)
Isn't a pointer an address itself. When I am passing a address, should it not work?

2)
If I try to change the above function prototype for passing pointer by reference, like

void BSTree::AddNode(int a, Node * & ptr )

i still get some error when calling it with statement

tree.AddNode(5,tree.getRoot());

The error says "No matching functio to call". I usually don't have to make any changes to 'function calling' when pass by reference is used. What is the appropriate way to make the two work together?

[doug4]

The problem I see is you never set root when you add the first node.

You probably should have 2 functions for AddNode instead of 1. AddNode(int a) would check to see if the root is null. If so, create a node and store it as root. If root is not null, call the other AddNode function, passing it the right or left branch pointer, as necessary (or just returning if a = root->getData()).

Edit: I think this is the same thing ne555 is trying to say, but with different words.

[ne555]

> Isn't a pointer an address itself. When I am passing a address, should it not work?
sure, if you take the address of the pointer.

void BSTree::AddNode(int value, Node ** ptr ){
   //...
   *ptr = new Node(value);
}

You are copying the pointer and modifying the copy, so the original remains unchanged.


> i still get some error when calling it
> The error says "No matching functio to call".
¿description of the function match?
¿candidates?
That information was (or should have) in the error message of your compiler. If you do not understand something that's more a reason to not edit it away.

You cannot bind a non-constant reference to a temporary.
`getRoot()' returns a copy of the root pointer, a temporary.


> I think this is the same thing ne555 is trying to say
no.