/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * This program demonstrates the use of the shell sort algorithm.  For
 * more information about this and other sorting algorithms, see
 * http://linux.wku.edu/~lamonml/kb.html
 *
 */

#include <stdlib.h>
#include <stdio.h>

#define NUM_ITEMS 100

void shellSort(int numbers[], int array_size);

int numbers[NUM_ITEMS];


int main()
{
  int i;

  //seed random number generator
  srand(getpid());

  //fill array with random integers
  for (i = 0; i < NUM_ITEMS; i++)
    numbers[i] = rand();

  //perform shell sort on array
  shellSort(numbers, NUM_ITEMS);

  printf("Done with sort.\n");

  for (i = 0; i < NUM_ITEMS; i++)
    printf("%i\n", numbers[i]);
}


void shellSort(int numbers[], int array_size)
{
  int i, j, increment, temp;

  increment = 3;
  while (increment > 0)
  {
    for (i=0; i < array_size; i++)
    {
      j = i;
      temp = numbers[i];
      while ((j >= increment) && (numbers[j-increment] > temp))
      {
        numbers[j] = numbers[j - increment];
        j = j - increment;
      }
      numbers[j] = temp;
    }
    if (increment/2 != 0)
      increment = increment/2;
    else if (increment == 1)
      increment = 0;
    else
      increment = 1;
  }
}