Multipurpose sorting program using function pointers. - C++ Function

C++ examples for Function:Function Pointer

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Description

Multipurpose sorting program using function pointers.

Demo Code

#include <iostream> 
#include <iomanip> 
using namespace std; 

// prototypes /*from   w  w w .  j  av a  2  s.  com*/
void selectionSort( int [], const int, bool (*)( int, int ) ); 
void swap( int * const, int * const ); 
bool ascending( int, int ); // implements ascending order 
bool descending( int, int ); // implements descending order 

int main() 
{ 
   const int arraySize = 10; 
   int order; // 1 = ascending, 2 = descending 
   int counter; // array index 
   int a[ arraySize ] = { 122, 612, 4, 8, 10, 12, 89, 68, 45, 37 }; 

   cout << "Enter 1 to sort in ascending order,\n" 
       << "Enter 2 to sort in descending order: "; 
   cin >> order; 

   for ( counter = 0; counter < arraySize; ++counter ) 
       cout << setw( 4 ) << a[ counter ]; 

   if ( order == 1 ) 
   { 
       selectionSort( a, arraySize, ascending ); 
       cout << "\nData items in ascending order\n"; 
   }else { 
       selectionSort( a, arraySize, descending ); 
       cout << "\nData items in descending order\n"; 
   }

   for ( counter = 0; counter < arraySize; ++counter ) 
       cout << setw( 4 ) << a[ counter ]; 

   cout << endl; 
}

void selectionSort( int work[], const int size, bool (*compare)( int, int ) ) 
{ 
   int smallestOrLargest; // index of smallest (or largest) element 

   // loop over size - 1 elements 
   for ( int i = 0; i < size - 1; ++i ) 
   { 
       smallestOrLargest = i; // first index of remaining vector 

       // loop to find index of smallest (or largest) element 
       for ( int index = i + 1; index < size; ++index ) 
           if ( !(*compare)( work[ smallestOrLargest ], work[ index ] ) ) 
              smallestOrLargest = index; 

       swap( &work [ smallestOrLargest ], &work[ i ] ); 
   }
}

void swap( int * const element1Ptr, int * const element2Ptr ) 
{ 
   int hold = *element1Ptr; 
   *element1Ptr = *element2Ptr; 
   *element2Ptr = hold; 
}

bool ascending( int a, int b ) 
{ 
   return a < b; // returns true if a is less than b 
}
bool descending( int a, int b ) 
{ 
   return a > b; // returns true if a is greater than b 
}

Result


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