public static DirectedGraphBuilder <T> FromExistingGraph(IDirectedGraph <T> graph)
{
var builder = new DirectedGraphBuilder <T>();
foreach (var element in graph.Elements)
{
builder.elements.Add(element);
var successors = new HashSet <T>(graph.GetDirectSuccessorsOf(element));
var predecessors = new HashSet <T>(graph.GetDirectPredecessorsOf(element));
builder.directSuccessors.Add(element, successors);
builder.directPredecessors.Add(element, predecessors);
if (predecessors.Count == 0)
{
builder.sources.Add(element);
}
}
return(builder);
}