private static void ShortestPath()
        {
            string  filename       = "mediumEWD.txt";
            Scanner scanner        = new Scanner(new StreamReader(File.OpenRead(filename)));
            IEdgeWeightedDIgraph G = new EdgeWeightedDigraph(scanner);

            StdOut.Print("输入一个边:");
            int           s  = StdIn.ReadInt();
            IShortestPath sp = new DijkstraSP(G, s);

            for (int t = 0; t < G.V; t++)
            {
                StdOut.Print(s + " to " + t);
                StdOut.Printf(" ({0}): ", sp.DistTo(t));
                if (sp.HasPathTo(t))
                {
                    foreach (var e in sp.PathTo(t))
                    {
                        StdOut.Print(e + "  ");
                    }
                }
                StdOut.Println();
            }
            DijkstraAllPairsSP allPairsSP = new DijkstraAllPairsSP(G);

            StdOut.Println();
            StdOut.Println(allPairsSP.Dist(1, 28));

            //string filename2 = "tinyEWDAG.txt";
            //scanner = new Scanner(new StreamReader(File.OpenRead(filename2)));
            //G = new EdgeWeightedDigraph(scanner);
            //IShortestPath sp2 = new AcyclicSP(G, s);
            //for (int t = 0; t < G.V; t++)
            //{
            //    StdOut.Print(s + " to " + t);
            //    StdOut.Printf(" ({0}): ", sp2.DistTo(t));
            //    if (sp2.HasPathTo(t))
            //        foreach (var e in sp.PathTo(t))
            //        {
            //            StdOut.Print(e + "  ");
            //        }
            //    StdOut.Println();
            //}

            //filename = "tinyEWDnc.txt";
            //scanner = new Scanner(new StreamReader(File.OpenRead(filename)));
            //G = new EdgeWeightedDigraph(scanner);
            //sp = new BellmanFordSP(G, s);
            //for (int t = 0; t < G.V; t++)
            //{
            //    StdOut.Print(s + " to " + t);
            //    StdOut.Printf(" ({0}): ", sp.DistTo(t));
            //    if (sp.HasPathTo(t))
            //        foreach (var e in sp.PathTo(t))
            //        {
            //            StdOut.Print(e + "  ");
            //        }
            //    StdOut.Println();
            //}
        }