public static IReadOnlyCollection <Point> ConvexHullGrahamScan(this IReadOnlyCollection <Point> points)
{
var zero = points.FindZeroPoint();
var comparer = new AngleDistanceComparer(zero);
var sortedPoints = points
.Where(p => p.NotEqualTo(zero))
.OrderBy(p => p, comparer)
.ToArray();
var convexHull = new List <Point> {
zero, sortedPoints.ElementAt(0)
};
for (var i = 1; i < sortedPoints.Length; i++)
{
convexHull.Add(sortedPoints.ElementAt(i));
convexHull.RemoveInnerConcavePoints();
}
convexHull.Add(zero);
convexHull.RemoveInnerConcavePoints();
convexHull.RemoveAt(convexHull.Count - 1);
return(convexHull);
}
private static Tuple <Tangent, Tangent> TangentsTo(this Point point, int indexOfPoint, Polygon polygon)
{
var angleComparer = new AngleDistanceComparer(point);
var sortedPoints = polygon
.Points
.Select((p, i) => new { p, i })
.OrderByDescending(o => o.p, angleComparer)
.ToArray();
var first = sortedPoints.First();
var last = sortedPoints.Last();
var leftTangent = new Tangent(point, indexOfPoint, first.p, first.i);
var rightTangent = new Tangent(point, indexOfPoint, last.p, last.i);
return(new Tuple <Tangent, Tangent>(leftTangent, rightTangent));
}
