Alg_20170628 non funziona

        public bool Alg_20170628(int a, int b, int c, int d)
        {
            var time = 0;
            var n_a = get_nodo(a);
            var n_b = get_nodo(b);
            var n_c = get_nodo(c);
            var n_d = get_nodo(d);

            Func<Nodo, Nodo, bool> IsAntenato = null;
            IsAntenato = (x, y) =>
            {
                if (y != null)
                {
                    if (x == y)
                        return true;
                    else
                        return IsAntenato(x, y.Pred);
                }

                return false;
            };

            Func<Nodo, bool> dfs = null;
            dfs = (u) =>
            {
                time++;
                u.discovered = time;
                u.color = Nodo.Color.Gray;

                foreach (var v in Adj[u])
                    if (v.color == Nodo.Color.White)
                    {
                        v.Pred = u;

                        if (!dfs(v))
                            return false;
                    }
                    else if (v.color == Nodo.Color.Gray)
                    {
                        if (n_d != v && IsAntenato(n_d, v))
                            return false;
                    }

                time++;
                u.finished = time;
                u.color = Nodo.Color.Black;

                return true;
            };


            n_b.color = Nodo.Color.Black;
            n_c.color = Nodo.Color.Black;

            var r = dfs(n_a);

            Console.WriteLine("Nel grafo {0}, {1}esiste un percorso {2} ~> {3} ~> {4} ~> {5}", Nome, (r ? "" : "Non "), a, b, c, d);

            return r;
        }