asked on

Binary Tree

I'm finding it hard do debug the attached code that constructs a binary search tree.
Please let me know what I am missing.

Thanks!

treeNode* constructBinaryTree()
{
	treeNode **root = new treeNode*;
	treeNode *current = new treeNode;
	//root = NULL;
	//current = NULL;
	int data = 0;

	while( data!= -1)
	{
		printf("\n\nEnter a value (Enter -1 to stop): ");
		scanf("%d", &data);

		treeNode *newNode = new treeNode;
		newNode->left = NULL;
		newNode->right = NULL;
		newNode->data = data;

		if(!current)
		{
			*root = newNode;
		}
		else
		{
			current = *root;
			while(current->left || current->right)
			{
				if(data<=current->data)
					current = current->left;
				else 
					current = current->right;
			}
			if(data<=current->data)
					current->left = newNode;
			else 
				current->right = newNode;
		}
	}

	return *root;
}

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#include <iostream>
#include <conio.h>
#pragma once

typedef struct treeNode
{
	struct treeNode *left;
	struct treeNode *right;
	int data;
} treeNode;

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Superdave

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dshrenik

ASKER

Thank you!

Can you tell me why I must not initialize them to NULL, and why I must not use "new" to declare them?

It is working better now, but not for all inputs. When I enter 3, 4, 5, -1 it creates the tree without any problems.

When I enter 3, 4, 1, then I get an exception : "Access violation reading location 0x00000000."

dshrenik

ASKER

My code now looks like this:

dshrenik

ASKER

This code now works:

Thanks!

#include <iostream>
#include <conio.h>
#include "treeNode.h"
#pragma once

treeNode* constructBinaryTree()
{
	treeNode *root = new treeNode;
	treeNode *current = new treeNode;
	treeNode *previous = new treeNode;
	root = NULL;
	current = NULL;
	previous = NULL;
	int data;

	while(1)
	{
		printf("\n\nEnter a value (Enter -1 to stop): ");
		scanf("%d", &data);
		if(data==-1)
			break;

		treeNode *newNode = new treeNode;
		newNode->left = NULL;
		newNode->right = NULL;
		newNode->data = data;

		current = root;
		previous = root;
		
		if(!current)
		{
			root = newNode;
		}
		else
		{			
			while(current)
			{
				previous = current;

				if(data <= current->data)
					current = current->left;
				else 
					current = current->right;
			}
			if(data<=previous->data)
					previous->left = newNode;
			else 
				previous->right = newNode;
		}
	}

	return root;
}

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