C++ Binary Search Tree status access violation error with adding nodes - c++

Question

I'm working on a program that works with a binary tree. I'm getting an error with adding new nodes into the tree. I can add one node, but after adding another, I get a STATUS_ACCESS_VIOLATION error. I think the error could be with the function arguments dealing with the search function. Please help me if you can.
Here is he .h file that i've written:
#ifndef P4_H
#define P4_H
#include <iostream>
#include <iomanip>
#include <fstream>
#include <cctype>
#include <string>
using namespace std;
struct TreeNode //ListNode structure with components
{
int acctNum;
TreeNode *left;
TreeNode *right;
};
typedef TreeNode* nodePtr; //defines a pointer to a treenode struct
class Tree
{
private:
nodePtr root;
int numElements;
public:
Tree()
{ root = NULL; numElements = 0; }
bool treeEmpty()
{ return (numElements == 0); }
void addNode()
{
int key;
cout << "Enter account number to add: ";
cin >> key;
cout << endl << endl;
nodePtr location = NULL, parent = NULL, p = NULL;
bool found = searchTree(key, &location, &parent);
cout << found << " " << location << " " << parent << endl << endl;
if (found)
{
cout << "Error! Account number: " << key << " already exists within"
<< " the tree." << endl << endl;
}
else
{
if (parent == NULL)
{
root = new TreeNode;
root->acctNum = key;
}
else
{
if (parent->acctNum > key)
{
parent->left = new TreeNode;
p = parent->left;
p->acctNum = key;
}
else
{
parent->right = new TreeNode;
p = parent->right;
p->acctNum = key;
}
}
}
}
bool searchTree(int key, nodePtr *location, nodePtr *parent)
{
bool found = false;
nodePtr p = root;
*location = root;
parent = NULL;
while (p != NULL && !found)
{
*location = p;
if (key == p->acctNum)
found = true;
else if (key < p->acctNum)
{
*parent = p;
p = p->left;
}
else if (key > p->acctNum)
{
*parent = p;
p = p->right;
}
}
return found;
}
void deleteNode()
{
int key;
nodePtr location = NULL, parent = NULL;
cout << "Enter account number to delete: ";
cin >> key;
cout << endl << endl;
bool found = searchTree(key, &location, &parent);
if (!found)
{
cout << "Error! Account number: " << key << " was not found."
<< endl << endl;
}
else if (location->left != NULL && location->right != NULL)
{ //delete node with left and right subtrees
nodePtr leftmost = location->right, leftmostParent = NULL;
while (leftmost->left != NULL)
{
leftmostParent = leftmost;
leftmost = leftmost->left;
}
leftmost->left = location->left;
leftmost->right = location->right;
leftmostParent->left = NULL;
if (parent->acctNum > location->acctNum)
parent->left = leftmost;
else
parent->right = leftmost;
delete location;
location = NULL;
}
else if (location->left != NULL && location->right == NULL)
{ //delete node with only a left subtree
if (parent->acctNum > location->acctNum)
parent->left = location->left;
else
parent->right = location->left;
delete location;
location = NULL;
}
else if (location->left == NULL && location->right != NULL)
{ //delete node with only a right subtree
nodePtr leftmost = location->right, leftmostParent = NULL;
while (leftmost->left != NULL)
{
leftmostParent = leftmost;
leftmost = leftmost->left;
}
leftmost->right = location->right;
leftmostParent->left = NULL;
if (parent->acctNum > location->acctNum)
parent->left = leftmost;
else
parent->right = leftmost;
delete location;
location = NULL;
}
else
{ //delete a leaf node
if (location->acctNum > parent->acctNum)
parent->right = NULL;
else
parent->left = NULL;
delete location;
location = NULL;
}
}
void displayAscend(nodePtr p, int count)
{
if (p->left != NULL)
displayAscend(p->left, count);
cout << count << ". " << p->acctNum << endl;
count ++;
if (p->right != NULL)
displayAscend(p->right, count);
}
void displayDescend(nodePtr p, int count)
{
if (p->right != NULL)
displayAscend(p->right, count);
cout << count << ". " << p->acctNum << endl;
count ++;
if (p->left != NULL)
displayAscend(p->left, count);
}
void readFile()
{
char filename[50];
cout << "Enter name of file to open: ";
cin.getline(filename,51);
cout << endl << endl;
ifstream inFile;
inFile.open(filename);
while (!inFile)
{
cout << "Error opening file! Please try again." << endl << endl;
cout << "Enter name of file: ";
cin.getline(filename,51);
cout << endl << endl;
}
int num;
while (!inFile.eof())
{
inFile >> num;
nodePtr location = NULL, parent = NULL, p = NULL;
bool found = searchTree(num, &location, &parent);
if (found)
{
cout << "Error! Account number: " << num << " already exists"
<< " within the tree." << endl << endl;
}
else
{
if (parent == NULL)
{
root = new TreeNode;
root->acctNum = num;
}
else
{
if (parent->acctNum > num)
{
parent->left = new TreeNode;
p = parent->left;
p->acctNum = num;
}
else
{
parent->right = new TreeNode;
p = parent->right;
p->acctNum = num;
}
}
}
}
}
};
#endif

Answer 1

In searchTree, you set parent to NULL before the loop, then dereference it in the loop.