CS153/hw4/hw4programs/qsort.oat

void quick_sort( int[] a, int l, int r)
{
   var j=0;

   if( l < r ) 
   {
      /* divide and conquer */
      j = partition( a, l, r);
      quick_sort( a, l, j-1);
      quick_sort( a, j+1, r);
   }
	
   return;
}

int partition( int[] a, int l, int r) {
   var pivot=a[l];
   var i =l;
   var j = r+1;
   var t=0; 
   var done = 0;
     	
   while(done==0)
   {
      i = i + 1;
      while( a[i] <= pivot & i <= r ) {
        i = i + 1;
      }	
      j = j - 1;
      while( a[j] > pivot ) {
        j = j - 1;
      }	
      if( i >= j ) { done=1; }
      if (done==0) {
        t = a[i]; a[i] = a[j]; a[j] = t;
      }
   }
   t = a[l]; a[l] = a[j]; a[j] = t;
   return j;
}

int program (int argc, string[] argv) {

  var a = new int[]{ 107, 112, 121, 102, 123, 115, 104, 111, 109};

  print_string (string_of_array (a));
  quick_sort( a, 0, 8);
  print_string (string_of_array (a));  

  return 255;
}