/// <summary>
/// Sorts points by angle, relative to the center
/// Time complexity O(N*logN)
/// </summary>
public static IList <PointInt2D> SortByAngle(IList <PointInt2D> points, PointInt2D center)
{
return(points.OrderBy(p => p, new MyComparer <PointInt2D>((a, b) =>
{
if (a.Y >= center.Y && b.Y < center.Y)
{
return -1;
}
if (b.Y >= center.Y && a.Y < center.Y)
{
return 1;
}
if (a.Y == center.Y && b.Y == center.Y)
{
if (a.X >= center.X)
{
if (b.X >= center.X)
{
return a.X.CompareTo(b.X);
}
return -1;
}
else
{
if (b.X >= center.X)
{
return 1;
}
return -a.X.CompareTo(b.X);
}
}
var cross = (a - center) * (b - center);
if (cross > 0)
{
return -1;
}
return cross < 0 ? 1 : (a - center).DistSq().CompareTo((b - center).DistSq());
})).ToList());
}
/// <summary> /// Gets doubled square of the given triangle /// </summary> public static long TriangleDoubledSquare(PointInt2D p1, PointInt2D p2, PointInt2D p3) => Math.Abs((p2 - p1) * (p3 - p1));