/// <summary>
/// following H.A.D Nascimento and P. Eades "User Hints for Directed Graph Drawing"
/// </summary>
/// <param name="graphForCycleRemoval">graphForCycleRemoval is connected</param>
/// <returns></returns>
IEnumerable<IEdge> GetFeedbackEdgeSet(GraphForCycleRemoval graphForCycleRemoval) {
graphForCycleRemoval.Initialize();
//empty at the end of the method
List<int> sl = new List<int>(); //sl - the sequence left part
List<int> sr = new List<int>(); //sr - the sequence right part. In our case it is a reversed right part
while (!graphForCycleRemoval.IsEmpty()) {
int u;
while (graphForCycleRemoval.TryGetSink(out u)) {
graphForCycleRemoval.RemoveNode(u);
sr.Add(u);
}
while (graphForCycleRemoval.TryGetSource(out u)) {
graphForCycleRemoval.RemoveNode(u);
sl.Add(u);
}
if (graphForCycleRemoval.TryFindVertexWithNoIncomingConstrainedEdgeAndMaximumOutDegreeMinusInDedree(out u)) {
graphForCycleRemoval.RemoveNode(u);
sl.Add(u);
}
}
Dictionary<int, int> S = new Dictionary<int, int>(sl.Count + sr.Count);
int j=0;
foreach (int u in sl)
S[u] = j++;
for (int i = sr.Count - 1; i >= 0; i--)
S[sr[i]] = j++;
foreach (IntPair pair in graphForCycleRemoval.GetOriginalIntPairs())
{
if (S[pair.First] > S[pair.Second])
yield return pair;
}
}
GraphForCycleRemoval CreateGraphForCycleRemoval(IEnumerable<int> componentNodes) {
GraphForCycleRemoval graphForCycleRemoval = new GraphForCycleRemoval();
foreach (int i in componentNodes) {
foreach (TEdge edge in this.graph.OutEdges(i))
graphForCycleRemoval.AddEdge(new IntPair(edge.Source,edge.Target));
foreach (IntPair intPair in this.graphOfConstraints.OutEdges(i))
graphForCycleRemoval.AddConstraintEdge(intPair);
}
return graphForCycleRemoval;
}