public void Combine(DisTreeItem second)
{
//get both roots
DisTreeItem rootA = this.Root();
DisTreeItem rootB = second.Root();
//if both share root, do nothing, already combined
if (rootA == rootB)
{
return;
}
//if A is bigger, attach B to A's root
if (rootA.Rank > rootB.Rank)
{
rootB.Parent = rootA;
}
//if B is bigger, attach A to B's root
else if (rootA.Rank < rootB.Rank)
{
rootA.Parent = rootB;
}
//if both trees are equal, parent B to A and upgrade A
else
{
rootB.Parent = rootA;
rootA.Rank++;
}
}
public static List <Vector3> PruneEdges(List <Vector3> Edges, float connectedness, IRandomProvider RNG)
{
//this random will be used for randomly adding back some pruned edges.
// System.Random RNG = new Random();
//this list will be returned.
List <Vector3> result = new List <Vector3>();
//sort edges by weight (stored in Vector3.Z)
List <Vector3> SortedEdges = Edges.OrderBy(v => v.Z).ToList();
//List of tree items
List <DisTreeItem> tree = new List <DisTreeItem>();
//list of nodes
//this implementation allows for arbitrary numeric indices
List <int> itemlist = new List <int>();
//find all possible nodes from the edges
foreach (Vector3 edge in SortedEdges)
{
//Get edge's start and end nodes
int A = (int)edge.X;
int B = (int)edge.Y;
//check if either already exists, add if not
if (!itemlist.Contains(A))
{
itemlist.Add(A);
}
if (!itemlist.Contains(B))
{
itemlist.Add(B);
}
}
//create a tree item from each found node
foreach (int i in itemlist)
{
tree.Add(new DisTreeItem(i));
}
//sort the tree by ID (node number) so we can tree[i]
tree = tree.OrderBy(v => v.ID).ToList();
//go through all edges starting with lowest
foreach (Vector3 edge in SortedEdges)
{
//get start and end node id
int A = (int)edge.X;
int B = (int)edge.Y;
//get the relevant tree items
DisTreeItem a = tree[A];
DisTreeItem b = tree[B];
//if the roots are different, the nodes connected by this edge belong to different trees
//this edge becomes part of the final spanning tree.
if (a.Root() != b.Root())
{
//merge the trees, smaller tree gets attached to the larger one.
a.Combine(b);
result.Add(edge);
}
//otherwise the edge creates a cycle and should be discarded
else
{
//however, a certain percentage is kept to keep things interesting
if (connectedness > RNG.NextFloat())
{
//we do not update the tree here
result.Add(edge);
}
}
}
return(result);
}
public DisTreeItem(int ID)
{
this.Rank = 0;
this.ID = ID;
this.Parent = this;
}
