Hey everybody,
So I though that I understood linked lists and arrays well enough to make a hash table with separate chaining. Theoretically, it seems trivial, but I am getting a runtime error.
The error appears to arise from the line head = heads, where head is a node pointer and heads is an array of node pointers.
When I tried to go through this issue with my debugger, all I got was an indecipherable 'Unhandled Exception' error and a runtime crash.
The node that I am using holds an instance of a class Person as its data member and the phone number string member of Person is used as the key.
Here is the code for the HashTable class and my main function with basic tests cases.
The error appears to occur at line 98:
#include <iostream>
#include <cmath>
#include <stdio.h>
#include <string>
#include "person.h"
using namespace std;
//typedef hashItemType Person;
/*
class ChainNode{
private:
ChainNode(Person & nodeItem, ChainNode *nextNode = NULL) : item(nodeItem), next(nextNode) {}
Person item;
ChainNode * next;
friend class HashTable;
};//end ChainNode class
*/
class HashTable {
public:
struct node {
Person item;
node * next;
};
//HashTable();
//implement destructor
bool tableIsEmpty() const;
int tableGetLength() const;
void tableInsert(Person newItem);
void tableDelete(string key);
Person tableRetrieve(string key);
int hash(string&);
protected:
int hashIndex(string key) const;
private:
static const int HASH_TABLE_SIZE = 101;
//typedef ChainNode * HashTableType[HASH_TABLE_SIZE];
//HashTableType table;
node * heads[HASH_TABLE_SIZE];
int size;
};//end HashTable
Person HashTable::tableRetrieve(string key)
{
int i = hash(key);
//ChainNode * p;
//p = table[i];
node * head = heads[i];
while( (head != NULL) && (head->item.getPhonenumber() != key))
{
head = head->next;
}//end while
if(head == NULL)
{
cout << "No values with that key" << endl;
exit(1);
}//end if
else{
return head->item;
}//end else
}
int HashTable::hash(string &key)
{
int hashVal = 0;
for(int i = 0; i< key.size(); i++)
{
hashVal = 37*hashVal+key[i];
hashVal %= HASH_TABLE_SIZE;
if(hashVal < 0)
{
hashVal += HASH_TABLE_SIZE;
}
return hashVal;
}//end for
}//end hash
void HashTable::tableInsert(Person newitem)
{
cout << "inside function" << endl;
string key = newitem.getPhonenumber();
cout << "got key" << endl;
int i = hash(key);
cout << i << endl;
cout << "got index" << endl;
//ChainNode * p;
node * head = new node;
head = heads[i];
cout << "created new node" << endl;
head->item = newitem;
cout << "birds" << endl;
head->next = heads[i];
heads[i] = head;
}
int main() {
HashTable ht;
Person p;
p.setGPA("4.0");
p.setName("Bubba");
p.setPhonenumber("4443");
ht.tableInsert(p);
return 0;
}and here is the code for the Person class:
#include <iostream>
#include <cstdlib>
#include <fstream>
#include <iomanip>
#include <stdio.h>
#include <string>
using namespace std;
class Person{
private:
string name;
string phonenumber;
string GPA;
public:
Person();
Person(string name, string phonenumber);
string getName();
string getPhonenumber();
void setName(string newname);
void setPhonenumber(string newphonenumber);
void setGPA(string);
string getGPA();
};
Person::Person()
{
}
Person::Person(string newname, string newphonenumber)
{
name = newname;
phonenumber = newphonenumber;
}
string Person::getName() {
return name;
}
string Person::getPhonenumber() {
return phonenumber;
}
void Person::setName(string newname) {
name = newname;
}
void Person::setPhonenumber(string newphonenumber) {
phonenumber = newphonenumber;
}
string Person::getGPA() {
return GPA;
}//end
void Person::setGPA(string newGPA) {
GPA = newGPA;
}//endAny input anybody has on what is going wrong would be greatly appreciated. I'm pretty stumped at this point.
