BinaryTree Template Crashes - c++

Question

Can anyone tell me why my last function height() causes the system to crash? I tested every function and they all work but when I coded this one and called it from main it causes the program to crash. It builds without any errors.
#ifndef BINARYTREE_H
#define BINARYTREE_H
#include <iostream>
using namespace std;
// This class is a template class that creates a binary
// tree that can hold values of any data type. It has
// functions to insert a node, delete a node, display the
// tree In Order, Pre Order and Post Order, search for a
// value, count the number of total nodes, left nodes,
// and a function to determine the height of the tree.
template <class T>
class BinaryTree
{
private:
struct TreeNode
{
T value; // The value in the node
TreeNode *left; // Pointer to left child node
TreeNode *right; // Pointer to right child node
};
TreeNode *root; // Pointer to the root node
// Private member functions
void insert(TreeNode *&, TreeNode *&);
void destroySubTree(TreeNode *);
void deleteNode(T, TreeNode *&);
void makeDeletion(TreeNode *&);
void displayInOrder(TreeNode *) const;
void displayPreOrder(TreeNode *) const;
void displayPostOrder(TreeNode *) const;
int counter(TreeNode *);
int leafCounter(TreeNode *);
int height(TreeNode *);
public:
// Constructor
BinaryTree()
{ root = NULL; }
// Destructor
~BinaryTree()
{ destroySubTree(root); }
// Binary tree operations
void insertNode(T);
bool searchNode(T);
void remove(T);
void displayPreOrder() const
{ displayPreOrder(root); }
void displayInOrder() const
{ displayInOrder(root); }
void displayPostOrder() const
{ displayPostOrder(root); }
// Node counter
int counter()
{
int n = counter(root);
return n;
}
// Leaf counter
int leafCounter()
{
int leaf = leafCounter(root);
return leaf;
}
// Height of the tree
int height()
{
int h = height(root);
return h;
}
};
//*********************************************************
// insert function accepts a TreeNode pointer and a *
// pointer to a node. The function inserts the node into *
// the tree pointer to by the TreeNode pointer. This *
// function is call recursively. *
//*********************************************************
template <class T>
void BinaryTree<T>::insert(TreeNode *&nodePtr, TreeNode *&newNode)
{
if (nodePtr == NULL)
nodePtr = newNode; // Insert the node
else if (newNode->value < nodePtr->value)
insert(nodePtr->left, newNode); // Search the left branch
else
insert(nodePtr->right, newNode);// Search the right branch
}
//*********************************************************
// insertNode creates anew node to hold num as its value *
// and passes it to the insert function. *
//*********************************************************
template <class T>
void BinaryTree<T>::insertNode(T item)
{
TreeNode *newNode; // Pointer to a new node
// Create anew node and store num in it
newNode = new TreeNode;
newNode->value = item;
newNode->left = newNode->right = NULL;
// Insert the node
insert(root, newNode);
}
//**********************************************************
// destroySubTree is called by the destructor. It deletes *
// all nodes in the tree. *
//**********************************************************
template <class T>
void BinaryTree<T>::destroySubTree(TreeNode *nodePtr)
{
if (nodePtr)
{
if (nodePtr->left)
destroySubTree(nodePtr->left);
if (nodePtr->right)
destroySubTree(nodePtr->right);
delete nodePtr;
}
}
//**********************************************************
// searchNode determines if a value is present in the tree.*
// If so, the function returns true. Otherwise it returns *
// false.
//**********************************************************
template <class T>
bool BinaryTree<T>::searchNode(T item)
{
TreeNode *nodePtr = root;
while (nodePtr)
{
if (nodePtr->value == item)
return true;
else if (item < nodePtr->value)
nodePtr = nodePtr->left;
else
nodePtr = nodePtr->right;
}
return false;
}
//*********************************************************
// remove calls deleteNode to delete the node whode value *
// member is the same as num *
//*********************************************************
template <class T>
void BinaryTree<T>::remove(T item)
{
deleteNode(item, root);
}
//*********************************************************
// deleteNode deletes the node whose value member is the *
// same as num *
//*********************************************************
template <class T>
void BinaryTree<T>::deleteNode(T item, TreeNode *&nodePtr)
{
if (item < nodePtr->value)
deleteNode(item, nodePtr->left);
else if (item > nodePtr->value)
deleteNode(item, nodePtr->right);
else
makeDeletion(nodePtr);
}
//*********************************************************
// makeDeletion takes a reference to apointer to the node *
// that is to be deleted. The node is removed and the *
// branches of the tree below the node are reattached *
//*********************************************************
template <class T>
void BinaryTree<T>::makeDeletion(TreeNode *&nodePtr)
{
// Define a temporary pointer to use in reattaching
// the left subtree
TreeNode *tempNodePtr;
if (nodePtr == NULL)
cout << "Cannot delete empty node.\n";
else if (nodePtr->right == NULL)
{
tempNodePtr = nodePtr;
nodePtr = nodePtr->left; // Reattach the left child
delete tempNodePtr;
}
else if (nodePtr->left == NULL)
{
tempNodePtr = nodePtr;
nodePtr = nodePtr->right; // Reattach the right child
delete tempNodePtr;
}
}
//*********************************************************
// The displayInOrder function displays the values in the *
// subtree pointed to by nodePtr, via inorder traversal *
//*********************************************************
template <class T>
void BinaryTree<T>::displayInOrder(TreeNode *nodePtr) const
{
if (nodePtr)
{
displayInOrder(nodePtr->left);
cout << nodePtr->value << endl;
displayInOrder(nodePtr->right);
}
}
//*********************************************************
// The displayPreOrder function displays the values in the*
// subtree pointed to by nodePtr, via Preorder traversal *
//*********************************************************
template <class T>
void BinaryTree<T>::displayPreOrder(TreeNode *nodePtr) const
{
if (nodePtr)
{
cout << nodePtr->value << endl;
displayInOrder(nodePtr->left);
displayInOrder(nodePtr->right);
}
}
//*********************************************************
// displayPostOrder function displays the values in the *
// subtree pointed to by nodePtr, via Postorder traversal *
//*********************************************************
template <class T>
void BinaryTree<T>::displayPostOrder(TreeNode *nodePtr) const
{
if (nodePtr)
{
displayInOrder(nodePtr->left);
displayInOrder(nodePtr->right);
cout << nodePtr->value << endl;
}
}
//*********************************************************
// counter counts the number of nodes the tree has *
//*********************************************************
template <class T>
int BinaryTree<T>::counter(TreeNode *nodePtr)
{
if (nodePtr == NULL)
return 0;
else
return counter(nodePtr->left) +1+ counter(nodePtr->right);
}
//*********************************************************
// leafCounter counts the number of leaf nodes in the tree*
//*********************************************************
template <class T>
int BinaryTree<T>::leafCounter(TreeNode *nodePtr)
{
if (nodePtr == NULL)
return 0;
else if (nodePtr->left == NULL && nodePtr->right == NULL)
return 1;
else
return leafCounter(nodePtr->left) + leafCounter(nodePtr->right);
}
//*********************************************************
// height returns the height of the tree *
//*********************************************************
template <class T>
int BinaryTree<T>::height(TreeNode *nodePtr)
{
if(nodePtr = NULL)
return -1;
if (height(nodePtr->left) <= height(nodePtr->right))
return (height(nodePtr->right) +1);
else
return (height(nodePtr->left) +1);
}
#endif
Main
// This program demonstrates that the functions of
// BinaryTree works correctly.
#include "BinaryTree.h"
#include <iostream>
using namespace std;
int main()
{
// Create a BinaryTree object
BinaryTree<int> tree;
// Insert some nodes
cout << "Inserting nodes...\n";
tree.insertNode(5);
tree.insertNode(10);
tree.insertNode(3);
tree.insertNode(1);
tree.insertNode(13);
// Display the nodes InOrder
cout << "\nDisplaying the nodes InOrder...\n";
tree.displayInOrder();
// Display the nodes PreOrder
cout << "\nDisplaying the nodes PreOrder...\n";
tree.displayPreOrder();
// Display the nodes PostOrder
cout << "\nDisplaying the nodes PostOrder...\n";
tree.displayPostOrder();
// Delete a node
cout << "\nDeleting node 3...\n";
tree.remove(3);
// Display the nodes after deletion
cout << "\nHere are the nodes InOrder after deletion:\n";
tree.displayInOrder();
// Search the nodes for the value 10
cout << "\nSearching the nodes for the value 10...\n";
if (tree.searchNode(10))
cout << "Value was found.\n";
else
cout << "Value was not found.\n";
// Search for the deleted node 3
cout << "\nSearching for the deleted node 3...\n";
if (tree.searchNode(3))
cout << "Value was found.\n";
else
cout << "Value was not found.\n";
// Count how many nodes are in the tree
cout << "\nThere are " << tree.counter() << " nodes"
<< " in the tree.\n";
// Count how many leafs are in the tree
cout << "\nThere are " << tree.leafCounter()
<< " leaves in the tree.\n";
// Get the height of the tree
cout << "\nThe height of the tree is " << tree.height();
cout << endl;
return 0;
}

Answer 1

if(nodePtr = NULL)
should be:
if(nodePtr == NULL)
The first one sets nodePtr to NULL, then implicitly tests if the result is not NULL (which is always false). The second one tests whether nodePtr is NULL.