/// <summary>
/// Topologically sorts nodes in a given graph. If no <paramref name="nodes"/> are specified all nodes in the graph
/// are used (<see cref="IReadonlyDirectedGraph.Nodes"/>); if <paramref name="nodes"/> are specified, they must all
/// belong to the given <paramref name="graph"/>.
///
/// Returns a multi-value dictionary with keys ranging from 0 to max node height.
/// </summary>
public static MultiValueDictionary <int, NodeId> TopSort(this IReadonlyDirectedGraph graph, IEnumerable <NodeId> nodes = null)
{
nodes = nodes ?? graph.Nodes;
MultiValueDictionary <int, NodeId> nodesByHeight = new MultiValueDictionary <int, NodeId>();
foreach (var node in nodes)
{
var height = graph.GetNodeHeight(node);
nodesByHeight.Add(height, node);
}
return(nodesByHeight);
}
private void VerifyNodeHeights(IReadonlyDirectedGraph graph, NodeId[] nodes)
{
XAssert.AreEqual(0, graph.GetNodeHeight(nodes[7]));
XAssert.AreEqual(0, graph.GetNodeHeight(nodes[10]));
XAssert.AreEqual(0, graph.GetNodeHeight(nodes[11]));
XAssert.AreEqual(1, graph.GetNodeHeight(nodes[8]));
XAssert.AreEqual(1, graph.GetNodeHeight(nodes[9]));
XAssert.AreEqual(2, graph.GetNodeHeight(nodes[3]));
XAssert.AreEqual(2, graph.GetNodeHeight(nodes[4]));
XAssert.AreEqual(2, graph.GetNodeHeight(nodes[5]));
XAssert.AreEqual(2, graph.GetNodeHeight(nodes[6]));
XAssert.AreEqual(3, graph.GetNodeHeight(nodes[0]));
XAssert.AreEqual(3, graph.GetNodeHeight(nodes[1]));
XAssert.AreEqual(3, graph.GetNodeHeight(nodes[2]));
}