public static IEnumerable <Vertex <TVertexId> > DfsTopologicalSort <TVertexId, TVertexProperty, TEdgeProperty>(
this IDirectedGraph <TVertexId, TVertexProperty, TEdgeProperty> graph)
{
if (graph.EdgesCount == 0)
{
return(graph.Vertices);
}
var strategy = new TopologicalStrategy <TVertexId>();
graph.DfsRecursive(strategy, graph.Vertices);
return(strategy.order.Reverse <Vertex <TVertexId> >());
}