C++ Programming Code Examples
C++ > Data Structures Code Examples
Program to Implement Hash Tables with Double Hashing
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/* Program to Implement Hash Tables with Double Hashing */
#include <iostream>
#include <cstdlib>
#define MIN_TABLE_SIZE 10
using namespace std;
/* Node Type Declaration */
enum EntryType {Legitimate, Empty, Deleted};
/* Node Declaration */
struct HashNode
{
int element;
enum EntryType info;
};
/* Table Declaration */
struct HashTable
{
int size;
HashNode *table;
};
/* Function to Genereate First Hash */
int HashFunc1(int key, int size)
{
return key % size;
}
/* Function to Genereate Second Hash */
int HashFunc2(int key, int size)
{
return (key * size - 1) % size;
}
/* Function to Initialize Table */
HashTable *initializeTable(int size)
{
HashTable *htable;
if (size < MIN_TABLE_SIZE)
{
cout<<"Table Size Too Small"<<endl;
return NULL;
}
htable = new HashTable;
if (htable == NULL)
{
cout<<"Out of Space"<<endl;
return NULL;
}
htable->size = size;
htable->table = new HashNode [htable->size];
if (htable->table == NULL)
{
cout<<"Table Size Too Small"<<endl;
return NULL;
}
for (int i = 0; i < htable->size; i++)
{
htable->table[i].info = Empty;
htable->table[i].element = NULL;
}
return htable;
}
/* Function to Find Element from the table */
int Find(int key, HashTable *htable)
{
int hashVal= HashFunc1(key, htable->size);
int stepSize= HashFunc2(key, htable->size);
while (htable->table[hashVal].info != Empty &&
htable->table[hashVal].element != key)
{
hashVal = hashVal + stepSize;
hashVal = hashVal % htable->size;
}
return hashVal;
}
/* Function to Insert Element into the table */
void Insert(int key, HashTable *htable)
{
int pos = Find(key, htable);
if (htable->table[pos].info != Legitimate )
{
htable->table[pos].info = Legitimate;
htable->table[pos].element = key;
}
}
/* Function to Rehash the table */
HashTable *Rehash(HashTable *htable)
{
int size = htable->size;
HashNode *table = htable->table;
htable = initializeTable(2 * size);
for (int i = 0; i < size; i++)
{
if (table[i].info == Legitimate)
Insert(table[i].element, htable);
}
free(table);
return htable;
}
/* Function to Retrieve the table */
void Retrieve(HashTable *htable)
{
for (int i = 0; i < htable->size; i++)
{
int value = htable->table[i].element;
if (!value)
cout<<"Position: "<<i + 1<<" Element: Null"<<endl;
else
cout<<"Position: "<<i + 1<<" Element: "<<value<<endl;
}
}
/* Main Contains Menu */
int main()
{
int value, size, pos, i = 1;
int choice;
HashTable *htable;
while(1)
{
cout<<"\n----------------------"<<endl;
cout<<"Operations on Double Hashing"<<endl;
cout<<"\n----------------------"<<endl;
cout<<"1.Initialize size of the table"<<endl;
cout<<"2.Insert element into the table"<<endl;
cout<<"3.Display Hash Table"<<endl;
cout<<"4.Rehash The Table"<<endl;
cout<<"5.Exit"<<endl;
cout<<"Enter your choice: ";
cin>>choice;
switch(choice)
{
case 1:
cout<<"Enter size of the Hash Table: ";
cin>>size;
htable = initializeTable(size);
break;
case 2:
if (i > htable->size)
{
cout<<"Table is Full, Rehash the table"<<endl;
continue;
}
cout<<"Enter element to be inserted: ";
cin>>value;
Insert(value, htable);
i++;
break;
case 3:
Retrieve(htable);
break;
case 4:
htable = Rehash(htable);
break;
case 5:
exit(1);
default:
cout<<"\nEnter correct option\n";
}
}
return 0;
}
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