/*
 * ISA 563, Spring 2011
 * Copyleft by Muhammad Abdulla
 */


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

/* 
 * qsort.c -- Illustrates the usage of dynamic memory allocation and call by reference.
 *
 * The qsort details are based on The Practice of Programming (pp: 32-34) by Brian W. Kernighan and Rob Pike
 */

/* swap: interchange v[i] and v[j] */
void swap( int v[], int i, int j )
{
  int tmp;
  tmp = v[i];
  v[i] = v[j];
  v[j] = tmp;
}

/* quicksort: sort v[0]..v[n-1] into increasing 
 * order 
 */
void quicksort( int v[], int n )
{
  int i = 0, last = 0;

  if ( n <= 1 ) {             /* nothing to do */
    return;
  }

  swap( v, 0, rand() % n );  /* move pivot elem 
                                to v[0] */
  for ( i = 1; i < n; i++ ) { /* partition */
    if ( v[i] < v[0] ) {
      swap( v, ++last, i );
    }
  }
  swap( v, 0, last );        /* restore pivot */
  quicksort( v, last );      /* sort smaller values */
  quicksort( v+last+1, n-last-1 );  /* sort larger values */
}

void print_array( const int array[], int elems )
{
  int i;
  printf("{ ");
  for ( i = 0; i < elems; i++ ) {
    printf( "%d ", array[i] );
  }
  printf("}\n");
}

int main( void )
{
   int  cap = 8;  // keep track of capacity
   int  size = 0; // number of items in the array 
   int  *nums;    // pointer to dynamic array of numbers
   char line[32]; // input buffer
   int  d;

   // allocate some memory for the pointer first
   nums = (int *) malloc(cap * sizeof(int));
   assert(nums != NULL);

   // Read in numbers. Increase memory if we run out of space.
   while ( fgets(line, sizeof(line), stdin) ) {
      d = atoi(line);
      nums[size++] = d;

      if ( size == cap ) { // increase buffer size if full
         cap *= 2;
         nums = realloc(nums, cap * sizeof(int));
         assert(nums != NULL);
      }
   }
 

   // print original, sort, and print sorted
   print_array(nums, size);
   quicksort(nums, size);
   print_array(nums, size);

  return 0;
}