static void _ReplaceNode(
BinarySearchTreeNode <T> node,
BinarySearchTreeNode <T> replacement
)
{
if (node.parent != null)
{
if (node.parent.left == node)
{
node.parent.left = replacement;
}
else
{
node.parent.right = replacement;
}
}
if (replacement != null)
{
replacement.parent = node.parent;
}
}
public override object Insert(
Arc arc,
IComparer comparer = null
)
{
if (comparer == null)
{
comparer = insertComparer;
}
if (root == null)
{
return(base.Insert(arc));
}
// find arc within beachline that intersects w/ new arc
BinarySearchTreeNode <Arc> intersectingArcNode = (BinarySearchTreeNode <Arc>)base.GetNode(arc, comparer);
Arc intersectingArc = GetNodeData(intersectingArcNode);
//Debug.Log("intersectingArcNode: " + intersectingArcNode + " intersectingArc: " + intersectingArc);
// edge is created between site of new arc and site of intersecting arc
var edge = new Edge(intersectingArc.site, arc.site);
// intersecting arc is replaced by three arcs and two breakpoints
var lowerArc = intersectingArc;
var middleArc = arc;
var upperArc = new Arc(intersectingArc.site);
var lowerBreakpoint = new Breakpoint(lowerArc, middleArc, edge, 0);
var upperBreakpoint = new Breakpoint(middleArc, upperArc, edge, 1);
// update breakpoints for each arc
if (lowerArc.upperBreakpoint != null)
{
var oldBreakpoint = lowerArc.upperBreakpoint;
var newBreakpoint = new Breakpoint(
upperArc,
oldBreakpoint.upperArc,
oldBreakpoint.edge,
oldBreakpoint.intersectionIndex);
upperArc.upperBreakpoint = newBreakpoint;
if (oldBreakpoint.upperArc != null)
{
oldBreakpoint.upperArc.lowerBreakpoint = newBreakpoint;
}
}
upperArc.lowerBreakpoint = upperBreakpoint;
middleArc.upperBreakpoint = upperBreakpoint;
middleArc.lowerBreakpoint = lowerBreakpoint;
lowerArc.upperBreakpoint = lowerBreakpoint;
//lowerArc.lowerBreakpoint remains intact
// insert new nodes
// this means that arc and upperArc are added as new nodes
// lowerArc is original arc
// new arc becomes parent of lower/upper arcs
// create new bst nodes
var arcNode = new BinarySearchTreeNode <Arc>(arc);
var upperArcNode = new BinarySearchTreeNode <Arc>(upperArc);
// link BST nodes
// arc node is the new parabola being added and becomes root of 3 node cluster
arcNode.parent = intersectingArcNode.parent;
arcNode.left = intersectingArcNode;
arcNode.right = upperArcNode;
if (arcNode.parent == null)
{
root = arcNode;
}
else
{
if (arcNode.parent.right == intersectingArcNode)
{
arcNode.parent.right = arcNode;
}
else
{
arcNode.parent.left = arcNode;
}
}
// upper arc is the new arc split from intersecting arc by new parabola
// left child is null, right child becomes original arc's right
upperArcNode.parent = arcNode;
upperArcNode.right = intersectingArcNode.right;
if (upperArcNode.right != null)
{
upperArcNode.right.parent = upperArcNode;
}
// lower arc is the original intersecting arc node
// left child remains intact, right is set to null
intersectingArcNode.parent = arcNode;
intersectingArcNode.right = null;
return(arcNode);
}