////   This file contains the C++ code from Program 16.15 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/pgm16_15.cpp//Digraph& FloydsAlgorithm (Digraph const& g){    using numeric_limits<unsigned int>::max;    unsigned int const n = g.NumberOfVertices ();    Array2D<unsigned int> distance (n, n);    for (Vertex::Number v = 0; v < n; ++v)	for (Vertex::Number w = 0; w < n; ++w)	    distance [v][w] = max ();    Iterator& p = g.Edges ();    while (!p.IsDone ())    {	WeightedEdge& edge = 	    dynamic_cast<WeightedEdge&> (*p);	Int& weight = dynamic_cast<Int&> (edge.Weight ());	distance [edge.V0 ()][edge.V1 ()] = weight;	++p;    }    delete &p;    for (Vertex::Number i = 0; i < n; ++i)	for (Vertex::Number v = 0; v < n; ++v)	    for (Vertex::Number w = 0; w < n; ++w)		if (distance [v][i] != max () &&		    distance [i][w] != max ())		{		    int const d =			distance [v][i] + distance [i][w];		    if (distance [v][w] > d)			distance [v][w] = d;		}    Digraph& result = *new DigraphAsMatrix (n);    for (Vertex::Number v = 0; v < n; ++v)	result.AddVertex (*new Vertex (v));    for (Vertex::Number v = 0; v < n; ++v)	for (Vertex::Number w = 0; w < n; ++w)	    if (distance [v][w] != max ())		result.AddEdge (*new WeightedEdge (		    result [v], result [w],		    *new Int (distance [v][w])));    return result;}