/* Quick sort. */

/* Quick sort. */
#include <stdio.h>
#include <conio.h>
int split ( int*, int, int ) ;
void main( )
{
 int arr[10] = { 11, 2, 9, 13, 57, 25, 17, 1, 90, 3 } ;
 int i ;
 void quicksort ( int *, int, int ) ;
 clrscr( ) ;
 printf ( "Quick sort.\n" ) ;
 printf ( "\nArray before sorting:\n") ;
 for ( i = 0 ; i <= 9 ; i++ )
  printf ( "%d\t", arr[i] ) ;
 quicksort ( arr, 0, 9 ) ;
 printf ( "\nArray after sorting:\n") ;
 for ( i = 0 ; i <= 9 ; i++ )
  printf ( "%d\t", arr[i] ) ;
 getch( ) ;
}
void quicksort ( int a[ ], int lower, int upper )
{
 int i ;
 if ( upper > lower )
 {
  i = split ( a, lower, upper ) ;
  quicksort ( a, lower, i - 1 ) ;
  quicksort ( a, i + 1, upper ) ;
 }
}
int split ( int a[ ], int lower, int upper )
{
 int i, p, q, t ;
 p = lower + 1 ;
 q = upper ;
 i = a[lower] ;
 while ( q >= p )
 {
  while ( a[p] < i )
   p++ ;
  while ( a[q] > i )
   q-- ;
  if ( q > p )
  {
   t = a[p] ;
   a[p] = a[q] ;
   a[q] = t ;
  }
 }
 t = a[lower] ;
 a[lower] = a[q] ;
 a[q] = t ;
 return q ;
}