ernie.WPI.EDU> cat select.C

// file select.C, cs2223, D97/98 //
// program which selection sorts an array

// 02Mar98 NW, First version

// global varaibles
int compares, swaps;

// includes
#include "headers.h"

// definitions
#define NMAX 10000

// prototypes
void selection(int, int *); // selection sort an array
void shuffle(int, int *); // shuffle the values in an array

// main
int main ()
	{
	extern int compares, swaps;
	int *array = new int[NMAX];
	srand(time(NULL)); // seed the random number generator
	
	for (int size = 1; size <= NMAX; size *= 10)
		{
		cout << endl << "n = " << size << endl;
		
		// best case - ascending order
		for (int i = 0; i < size; i++) array[i] = i + 1; // fill the array in ascending order
		compares = swaps = 0;
		selection(size, array); // selection sort
		cout << "   best compares = " << compares << ",   swaps = " << swaps << endl;
		
		// worst case - descending order
		for (int i = 0; i < size; i++) array[i] = size - i; // fill the array in descending order
		compares = swaps = 0;
		selection(size, array); // selection sort
		cout << "  worst compares = " << compares << ",   swaps = " << swaps << endl;
		} // end for(size)
		
	return 0;
	} // end main()

// functions
void selection(int n, int *array) // selection sort an array
	{
	extern int compares, swaps;
	int temp;
	for (int i = 0; i < n - 1; i++)
		for (int j = i + 1; j < n; j++)
			if (compares++, array[j] < array[i])
				{
				swaps++;
				temp = array[i]; // swap the values
				array[i] = array[j];
				array[j] = temp;
				}
	return;
	} // end selection()

void shuffle(int n, int *array) // shuffle the values in an array
	{
	for (int i = 0; i < n; i++)
		{
		int temp = array[i]; // swap each value with a random one
		int other = rand() % n;
		array[i] = array[other];
		array[other] = temp;
		}
	return;
	} // end shuffle()

// Copyright 1998 Norman Wittels

ernie.WPI.EDU> g++ select.C

ernie.WPI.EDU> a.out

n = 1
   best compares = 0,   swaps = 0
  worst compares = 0,   swaps = 0

n = 10
   best compares = 45,   swaps = 0
  worst compares = 45,   swaps = 45

n = 100
   best compares = 4950,   swaps = 0
  worst compares = 4950,   swaps = 4950

n = 1000
   best compares = 499500,   swaps = 0
  worst compares = 499500,   swaps = 499500

n = 10000
   best compares = 49995000,   swaps = 0
  worst compares = 49995000,   swaps = 49995000

ernie.WPI.EDU>