C2440 '=' cannot convert from 'int' to 'BST<int>::Node*

Question

BST.h

#include "stdafx.h"
#include <iostream>
#include <cstddef>
#include <string>
using namespace std;


#ifndef BST_H_
#define BST_H_

template <class bstdata>
class BST
{
private:
struct Node
{
    bstdata data;
    Node* left;
    Node* right;

    Node() : left(NULL), right(NULL){}
    Node(bstdata newdata) : left(NULL), right(NULL), data(newdata){}
};

typedef struct Node* Nodeptr;

Nodeptr root;
int size;

/** Private Helper Functions **/

void addValue(Nodeptr root, bstdata value);
void printInOrder(Nodeptr root);


public:
BST();
bool isEmpty();
int getSize();
void add(bstdata value);
bstdata getRoot();
void inOrderPrint();

};

/**Public functions*/

template <class bstdata>
BST<bstdata>::BST() : size(0), root(NULL){};

template <class bstdata>
void BST<bstdata>::add(bstdata value)
{
if (root == NULL)
{
    root = new Node(value);
    size++;
}
else
    addValue(root, value);
}

template <class bstdata>
void BST<bstdata>::addValue(Nodeptr root, bstdata value)
{
if (value == root->data)
    return;

if (value < root->data)
{
    if (root->left == NULL)
    {
        root->left = value;
        size++;
    }
}
else
    addValue(root-> left, value);

if (root-> right == NULL)
{
    root->left = value;
    size++;
}
else
    addValue(root-> right, value);
}

template <class bstdata>
bstdata BST<bstdata>::getRoot()
{
if (size == 0)
    cout << "getRoot: there is no root in the BST" << endl;
else
    return root->data;

}
#endif

BST.cpp

// BSTTest.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "BST.h"
#include <iostream>
#include <cstddef>
#include <string>
using namespace std;


int main()
{

BST<int> B;

B.add(5);

B.getRoot();

return 0;
}

So the error, the title of this post, I am getting happens twice. It is in the two lines that read: root->left = value; located in the addValue function in the header file. I am not sure why I can not assign the value to the pointer left. If anyone could help that could be great.

Answer 1

The lines

     root->left = value;

and

     root->left = value;

are not right. You cannot assign an object of type int to an object of type Node* .

They need to be

     root->left = new Node(value);

and

     root->left = new Node(value);

respectively.

Answer 2

Like your error says, the two types are incompatible. The template type is int (first line in main) and the type of left is Node* . Do you mean to say root->data = value ? Either that or you need to create a new Node , set its data to value and then assign the new node to root->left`.