/*
 * 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 heap 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 heapSort(int numbers[], int array_size);
void siftDown(int numbers[], int root, int bottom);

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 heap sort on array
  heapSort(numbers, NUM_ITEMS);

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

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


void heapSort(int numbers[], int array_size)
{
  int i, temp;

  for (i = (array_size / 2)-1; i >= 0; i--)
    siftDown(numbers, i, array_size);

  for (i = array_size-1; i >= 1; i--)
  {
    temp = numbers[0];
    numbers[0] = numbers[i];
    numbers[i] = temp;
    siftDown(numbers, 0, i-1);
  }
}


void siftDown(int numbers[], int root, int bottom)
{
  int done, maxChild, temp;

  done = 0;
  while ((root*2 <= bottom) && (!done))
  {
    if (root*2 == bottom)
      maxChild = root * 2;
    else if (numbers[root * 2] > numbers[root * 2 + 1])
      maxChild = root * 2;
    else
      maxChild = root * 2 + 1;

    if (numbers[root] < numbers[maxChild])
    {
      temp = numbers[root];
      numbers[root] = numbers[maxChild];
      numbers[maxChild] = temp;
      root = maxChild;
    }
    else
      done = 1;
  }
}