qsort-2.c

#include <stdio.h>
#include <string.h>
#include <unistd.h>

int comparisons = 0;

void display (char **name, char *pivot, int left, int right)
{
  printf ("\e[H\e[J");
  for (int i = 0; name[i]; i++)
    {
      printf ("%s", name[i]);
      if (name[i] == pivot)
        printf (" <==");
      else if (i == left || i == right)
        printf (" <--");
      printf ("\n");
    }
  printf ("%d\n", comparisons);
}

int compare (char **name, char *pivot, int left, int right)
{
  int result = strcmp (name[left], pivot);
  comparisons++;
  display (name, pivot, left, right);
  usleep (200000);
  return result;
}

void quicksort (char **name, int left, int right)
{
  int p = (left + right) / 2;
  char *pivot = name[p];
  int l = left;
  int r = right;
  while (l < r)
    {
      while (l < r && compare (name, pivot, l, r - 1) < 0)
        l++;
      while (l < r && compare (name, pivot, r - 1, l) > 0)
        r--;
      if (l < r)
        {
          char *temp = name[r - 1];
          name[r - 1] = name[l];
          name[l] = temp;
          l++;
          r--;
        }
    }
  if (l < right)
    quicksort (name, l, right);
}

void sort (char **name)
{
  int r = 0;
  while (name[r])
    r++;
  quicksort (name, 0, r);
}

int main (void)
{
  char *name[] = { "Otto", "Lisa", "Anna", "Heinrich", "Siegfried", "Peter",
                   "Dieter", "Hugo", "Berta", "Maria", "Fritz", "Box", "Hans",
                   "Thomas", "Ulrich", "Zacharias", NULL };
  sort (name);
  display (name, NULL, -1, -1);
  return 0;
}