programming-examples/c++/Others/SeparateChaining.cpp - Implementation for separate chaining.cpp
2019-11-15 12:59:38 +01:00

137 lines
3.7 KiB
C++

SeparateChaining.cpp - Implementation for separate chaining
#include "SeparateChaining.h"
#include <iostream.h>
/**
* Internal method to test if a positive number is prime.
* Not an efficient algorithm.
*/
bool isPrime( int n )
{
if( n == 2 || n == 3 )
return true;
if( n == 1 || n % 2 == 0 )
return false;
for( int i = 3; i * i <= n; i += 2 )
if( n % i == 0 )
return false;
return true;
}
/**
* Internal method to return a prime number at least as large as n.
* Assumes n > 0.
*/
int nextPrime( int n )
{
if( n % 2 == 0 )
n++;
for( ; !isPrime( n ); n += 2 )
;
return n;
}
/**
* Construct the hash table.
*/
template <class HashedObj>
HashTable<HashedObj>::HashTable( const HashedObj & notFound, int size )
: ITEM_NOT_FOUND( notFound ), theLists( nextPrime( size ) )
{
}
/**
* Insert item x into the hash table. If the item is
* already present, then do nothing.
*/
template <class HashedObj>
void HashTable<HashedObj>::insert( const HashedObj & x )
{
List<HashedObj> & whichList = theLists[ hash( x, theLists.size( ) ) ];
ListItr<HashedObj> itr = whichList.find( x );
if( itr.isPastEnd( ) )
whichList.insert( x, whichList.zeroth( ) );
}
/**
* Remove item x from the hash table.
*/
template <class HashedObj>
void HashTable<HashedObj>::remove( const HashedObj & x )
{
theLists[ hash( x, theLists.size( ) ) ].remove( x );
}
/**
* Find item x in the hash table.
* Return the matching item or ITEM_NOT_FOUND if not found
*/
template <class HashedObj>
const HashedObj & HashTable<HashedObj>::find( const HashedObj & x ) const
{
ListItr<HashedObj> itr;
itr = theLists[ hash( x, theLists.size( ) ) ].find( x );
if( itr.isPastEnd( ) )
return ITEM_NOT_FOUND;
else
return itr.retrieve( );
}
/**
* Make the hash table logically empty.
*/
template <class HashedObj>
void HashTable<HashedObj>::makeEmpty( )
{
for( int i = 0; i < theLists.size( ); i++ )
theLists[ i ].makeEmpty( );
}
/**
* Deep copy.
*/
template <class HashedObj>
const HashTable<HashedObj> &
HashTable<HashedObj>::operator=( const HashTable<HashedObj> & rhs )
{
if( this != &rhs )
theLists = rhs.theLists;
return *this;
}
/**
* A hash routine for string objects.
*/
int hash( const string & key, int tableSize )
{
int hashVal = 0;
for( int i = 0; i < key.length( ); i++ )
hashVal = 37 * hashVal + key[ i ];
hashVal %= tableSize;
if( hashVal < 0 )
hashVal += tableSize;
return hashVal;
}
/**
* A hash routine for ints.
*/
int hash( int key, int tableSize )
{
if( key < 0 ) key = -key;
return key % tableSize;
}