////   This file contains the C# code from Program 15.12 of//   "Data Structures and Algorithms//    with Object-Oriented Design Patterns in C#"//   by Bruno R. Preiss.////   Copyright (c) 2001--2002 by Bruno R. Preiss, P.Eng.  All rights reserved.////   http://www.brpreiss.com/books/opus6/programs/pgm15_12.txt//public class HeapSorter : AbstractSorter{    protected const int baseIndex = 1;    protected void BuildHeap()    {	for (int i = n / 2; i > 0; --i)	    PercolateDown(i, n);    }    // ...}