////   This file contains the C++ code from Program 10.18 of//   "Data Structures and Algorithms//    with Object-Oriented Design Patterns in C++"//   by Bruno R. Preiss.////   Copyright (c) 1998 by Bruno R. Preiss, P.Eng.  All rights reserved.////   http://www.pads.uwaterloo.ca/Bruno.Preiss/books/opus4/programs/pgm10_18.cpp//void MWayTree::Withdraw (Object& object){    if (IsEmpty ())	throw invalid_argument ("object not found");    unsigned int const index = FindIndex (object);    if (index != 0 && object == *key [index])    {	if (!subtree [index - 1U]->IsEmpty ())	{	    Object& max = subtree [index - 1U]->FindMax ();	    key [index] = &max;	    subtree [index - 1U]->Withdraw (max);	}	else if (!subtree [index]->IsEmpty ())	{	    Object& min = subtree [index]->FindMin ();	    key [index] = &min;	    subtree [index]->Withdraw (min);	}	else	{	    --numberOfKeys;	    delete subtree [index];	    for(unsigned int i = index; i <= numberOfKeys; ++i)	    {		key [i] = key [i + 1];		subtree [i] = subtree [i + 1];	    }	    if (numberOfKeys == 0)		delete subtree [0];	}    }    else	subtree [index]->Withdraw (object);}