quick.c

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/*
 * 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 quick 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>
//#include <process.h>

//#define NUM_ITEMS 10000

void quickSort(double numbers[], int array_size);
void q_sort(double numbers[], int left, int right);

//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 quick sort on array
  quickSort(numbers, NUM_ITEMS);

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

*/
void quickSort(double numbers[], int array_size)
{
  q_sort(numbers, 0, array_size - 1);
}



void q_sort(double numbers[], int left, int right)
{
  int pivot;
  double      l_hold, r_hold;

  l_hold = left;
  r_hold = right;
  pivot = (int) numbers[left];
  while (left < right)
  {
    while ((numbers[right] >= pivot) && (left < right))
      right--;
    if (left != right)
    {
      numbers[left] = numbers[right];
      left++;
    }
    while ((numbers[left] <= pivot) && (left < right))
      left++;
    if (left != right)
    {
      numbers[right] = numbers[left];
      right--;
    }
  }
  numbers[left] = pivot;
  pivot = left;
  left = (int) l_hold;
  right = (int) r_hold;
  if (left < pivot)
    q_sort(numbers, left, pivot-1);
  if (right > pivot)
    q_sort(numbers, pivot+1, right);
}