/// <summary>
/// Creates the join tree (or forest) of this hypergraph.
/// If the graph is not acylic, it returns null.
/// </summary>
public DynamicForest GetJoinTree()
{
if (!IsAcyclic)
{
return(null);
}
DynamicForest forest = new DynamicForest(edgeList.Length);
for (int eId = 0; eId < edgeList.Length; eId++)
{
forest.AddVertex();
}
for (int eId = 0; eId < edgeList.Length; eId++)
{
int gamma = ai.gamma[eId];
if (gamma < 0)
{
continue;
}
int parId = ai.R[gamma];
forest.SetParent(eId, parId);
}
return(forest);
}
private void PrepareTree()
{
int centerCount = 0;
List <int[]> allCenters = new List <int[]>(forest.NumberOfTrees);
int[] roots = forest.GetRoots();
foreach (int rId in roots)
{
int[] centers = forest.GetCenter(rId);
centerCount += centers.Length;
allCenters.Add(centers);
}
foreach (int[] centers in allCenters)
{
forest.SetToRoot(centers[0]);
}
if (centerCount > 1)
{
// Forest is not connected or has two centers.
// Add dummy root.
isDummyRoot = true;
rootId = forest.AddVertex();
foreach (int[] centers in allCenters)
{
foreach (int c in centers)
{
forest.SetParent(c, rootId);
}
}
}
else
{
isDummyRoot = false;
rootId = allCenters[0][0];
}
}