programming-examples/c++/Others/SeparateChaining.cpp - Implementation for separate chaining.cpp

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;
        }