public static LineSegment PointsClosestPairIterative(List <Point> points)
{
Point?a = null, b = null;
var queue = new PriorityQueue <Point>(new PointXCoordComparerInversed());
points.ForEach(p => queue.Add(p));
var t = new SkipList <Point>(new PointYCoordComparer())
{
new Point {
X = double.NegativeInfinity, Y = double.NegativeInfinity
},
new Point {
X = double.NegativeInfinity, Y = double.PositiveInfinity
}
};
var current = queue.Peek();
var firstActive = current;
var delta = double.PositiveInfinity;
while (queue.Count > 0)
{
var p = current;
queue.Remove(current);
if (queue.Count > 0)
{
current = queue.Peek();
}
var r = t.Ceiling(p);
var l = t.Previous(r);
UpdateDeltaOnRight(ref p, ref r, ref delta, t, ref a, ref b);
UpdateDeltaOnLeft(ref p, ref l, ref delta, t, ref a, ref b);
UpdateActivePoints(ref p, ref firstActive, t, delta);
t.Add(p);
}
return(new LineSegment(a ?? new Point(), b ?? new Point()));
}
private static void UpdateDeltaOnLeft(ref Point p, ref Point l, ref double delta, SkipList <Point> t, ref Point?a, ref Point?b)
{
var i = 0;
while (l != new Point(double.NegativeInfinity, double.NegativeInfinity) && (i < 4))
{
var dist = D(p, l);
if (dist < delta)
{
delta = dist;
a = p;
b = l;
}
l = t.Previous(l);
if (l == default(Point))
{
break;
}
i++;
}
}
