C++ Hash Table Program Hangs after Entering a Value - c++

Question

If you can follow my main below, I run the program, I am able to enter an integer, it finds the next prime number, then asks for data. Once I enter data once, the program hangs. Seems to be in an infinite loop, or something. It doesn't crash. When I pause it, it brings up read.c file with an arrow on line 256. Not sure what this means whatsoever. Any help would be much appreciated.
I have the following class and member function declarations in hashtable.h:
#ifndef HASHTABLE_H
#define HASHTABLE_H
#define TRUE 1
#define FALSE 0
#define VERBOSE 0x01
#define NON_VERBOSE 0x02
#include "linkedlist.h"
class hashTable{
public:
int keys;
int tableSize;
linkedList<int> **table;
hashTable(const int n);
//~hashTable();
void hash(int value);
int search(int value);
int divisionMethod(int value, int sizeOfTable);
int midSquareMethod(int value, int sizeOfTable);
int total();
void printHashTable();
int next_prime(int value, char flag);
};
// constructor
hashTable::hashTable(const int n){
linkedList<int> newList;
tableSize = next_prime(n, VERBOSE);
cout << "Table size is: " << tableSize << "\n"; // for debugging
system("pause"); // for debugging
table = new linkedList<int>*[tableSize];
for (int i = 0; i < tableSize; i++)
table[i] = { new linkedList<int> };
}
// Compute the Hash Function and "Hash" element into table
void hashTable::hash(int value){
table[value % tableSize]->addToHead(value);
keys++;
//divisionMethod(midSquareMethod(value, tableSize), tableSize)
}
// Simple Search Function
// Returns the element searched for if found, 0 otherwise
int hashTable::search(int value){
return(table[value % tableSize]->search(value));
}
// Divsion Method for producing a semi-unique key
int hashTable::divisionMethod(int value, int sizeOfTable){
int key;
key = value % sizeOfTable;
return(key);
}
// Middle Square Method for producing a semi-unique key
int hashTable::midSquareMethod(int value, int sizeOfTable){
int key;
key = ((value * value) & 0x0ff0) >> 4; // pick the middle 8 bits
return(key);
}
// Returns the total number of keys in the table
int hashTable::total(){
return(keys);
}
// Print the hash table (for demonstration purposes
void hashTable::printHashTable(){
int i = 0, valueToPrint;
while (i < tableSize){
cout << i << ": ";
valueToPrint = table[i]->removeFromHead();
while (valueToPrint != 0){
cout << valueToPrint << " -> ";
valueToPrint = table[i]->removeFromHead();
}
cout << "|" << endl;
i++;
}
}
int hashTable::next_prime(int value, char flag){
int FOUND = FALSE;
int n;
while (!FOUND) {
for (n = 2; (n * n) <= value && (value % n) != 0; ++n);
if ((n * n) <= value) {
if (flag == VERBOSE)
cout << value << " is divisible by " << n << "\n";
value++;
}
else {
if (flag == VERBOSE)
cout << "The next largest prime is " << value << "\n";
FOUND = TRUE;
}
}
return(value);
}
#endif
Here is my linkedlist.h:
#ifndef LINKEDLIST_H
#define LINKEDLIST_H
#include <iostream>
using namespace std;
template <class TYPE>
class Node{
public:
TYPE data;
Node* next;
// constructor
Node(TYPE const& x){
data = x;
next = NULL;
}
};
template <class TYPE>
class linkedList{
//struct Node{
// TYPE data;
// Node *next;
//};
public:
Node<TYPE> *head;
Node<TYPE> *tail;
int size;
// constructor
linkedList(){
head = NULL;
tail = NULL;
size = 0;
}
~linkedList();
void addToHead(TYPE value);
void addToTail(TYPE value);
TYPE removeFromHead();
TYPE removeFromTail();
TYPE search(TYPE searchData);
TYPE isEmpty();
};
//destructor
template <class TYPE>
linkedList<TYPE>::~linkedList(void){
while (head){
Node<TYPE> *temp = head;
head = head->next;
delete temp;
}
}
// Insert an element at the head (start) of the linked list
template <class TYPE>
void linkedList<TYPE>::addToHead(TYPE value){
Node<TYPE> *newNode = new Node<TYPE>(value);
if (isEmpty())
head = newNode;
else{
newNode->next = head;
head = newNode;
}
}
// Add an element to the tail (end) of the linked list
template <class TYPE>
void linkedList<TYPE>::addToTail(TYPE value){
Node<TYPE> *newNode = new Node<TYPE>(value);
Node *tempPtr;
if(isEmpty()){
head = newNode;
tail = newNode;
}
else{
tail->next = newNode;
tail = tail->next;
}
}
// Remove an element from start of Linked List
template <class TYPE>
TYPE linkedList<TYPE>::removeFromHead(){
TYPE tempValue;
Node<TYPE> *temp;
if (head){
tempValue = head->data;
temp = head;
if (head == tail)
head = tail = 0;
else
head = head->next;
delete temp;
return tempValue;
}
else
return 0;
}
// Remove an element from the end of the linked list
template <class TYPE>
TYPE linkedList<TYPE>::removeFromTail(){
TYPE tempValue;
Node *temp;
if (tail){
tempValue = tail->data;
if (head == tail){
delete head;
head = tail = 0;
}
else{
for (temp = head; temp->next != tail; temp = temp->next);
delete tail;
tail = temp;
tail->next = 0;
}
return tempValue;
}
else
return 0;
}
// Search for an element in the linked list
// Will return the element if found, otherwise it returns 0
template <class TYPE>
TYPE linkedList<TYPE>::search(TYPE searchData){
Node<TYPE> *temp;
temp = head;
while (temp->next != tail){
if (tail->data == searchData)
return searchData;
if (temp->data == searchData)
return searchData;
else
temp = temp->next;
}
return 0;
}
// isEmpty() function checks if head == NULL
template <class TYPE>
TYPE linkedList<TYPE>::isEmpty(){
return(head == NULL);
}
#endif
Here is my main:
#include "hashtable.h"
int main(){
int n, input;
cout << "Enter an integer: ";
cin >> n;
cout << "\n\n";
hashTable myHashTable(n);
cout << "Enter some values into the table:" << endl;
cin >> input;
while (input != 0){
myHashTable.hash(input);
cin >> input;
}
myHashTable.printHashTable();
}

Answer 1

Something must be wrong, you have in attribute of your hashTable class ... a hashTable pointer. It must be a linkedlist pointer, nop ?

Answer 2

I did find out what was causing all this. It was the way that I was implementing the linked lists in my array of pointers. Pretty much just programmer error from long nights. Of course there is a lot wrong with my code that I posted here, which I fixed it all, e.g. search function in my hash class, etc.,
Here is what I changed that pretty much fixed a good portion of my problem posted here:
hashTable::hashTable(const int n, char hFunction){
keys = 0;
hashFunction = hFunction;
tableSize = next_prime(n, VERBOSE);
cout << "Table size is: " << tableSize << "\n\n"; // for debugging
system("pause"); // for debugging
table = new linkedList<int>[tableSize];
I also changed my linkedList<int> **table to linkedList<int> *table. If anyone else needs any pointers on the rest of this NOW working hash function, just get a hold of me.