private static IEnumerable<DirectedEdge> FindSequence(Subgraph graph)
{
GraphComponent.SetVisited(graph.GetEdgeEnumerator(), false);
var startNode = FindLowestDegreeNode(graph);
var list = startNode.OutEdges.Edges;
var ie = list.GetEnumerator();
ie.MoveNext();
var startDE = ie.Current;
var startDESym = startDE.Sym;
var seq = new LinkedList<DirectedEdge>();
var pos = AddReverseSubpath(startDESym, null, seq, false);
while (pos != null)
{
DirectedEdge prev = pos.Value;
DirectedEdge unvisitedOutDE = FindUnvisitedBestOrientedDE(prev.FromNode);
if (unvisitedOutDE != null)
{
DirectedEdge toInsert = unvisitedOutDE.Sym;
pos = AddReverseSubpath(toInsert, pos, seq, true);
}
else pos = pos.Previous;
}
/*
* At this point, we have a valid sequence of graph DirectedEdges, but it
* is not necessarily appropriately oriented relative to the underlying geometry.
*/
return Orient(seq/*new ArrayList(seq.CastPlatform())*/);
}
private static Node FindLowestDegreeNode(Subgraph graph)
{
int minDegree = Int32.MaxValue;
Node minDegreeNode = null;
IEnumerator<Node> i = graph.GetNodeEnumerator();
while (i.MoveNext())
{
Node node = i.Current;
if (minDegreeNode == null || node.Degree < minDegree)
{
minDegree = node.Degree;
minDegreeNode = node;
}
}
return minDegreeNode;
}
/// <summary>
/// Tests whether a complete unique path exists in a graph
/// using Euler's Theorem.
/// </summary>
/// <param name="graph">The <see cref="Subgraph" /> containing the edges.</param>
/// <returns><c>true</c> if a sequence exists.</returns>
private static bool HasSequence(Subgraph graph)
{
int oddDegreeCount = 0;
IEnumerator i = graph.GetNodeEnumerator();
while(i.MoveNext())
{
Node node = (Node) i.Current;
if (node.Degree % 2 == 1)
oddDegreeCount++;
}
return oddDegreeCount <= 2;
}
