public static List <Point> ConvexHullGrahams(List <Point> points)
{
if (points.Count == 1)
{
return(points);
}
List <Point> outPoints = new List <Point>();
var(minPoint, idx) = HelperMethods.GetMinPoint(points, 'y');
var minVec = new Vector2D(new Point(minPoint.X + 1234, minPoint.Y));
points.Sort((a, b) =>
{
if (HelperMethods.CheckTurn(new Line(minPoint, a), b) == Enums.TurnType.Colinear)
{
return(Point.GetSqrDistance(a, minPoint).CompareTo(Point.GetSqrDistance(b, minPoint)));
}
return(minVec.AngleTo(new Vector2D(minPoint.VectorTo(a))).Degrees
.CompareTo(minVec.AngleTo(new Vector2D(minPoint.VectorTo(b))).Degrees));
});
for (int i = 1; i < points.Count - 1; ++i)
{
if (HelperMethods.CheckTurn(new Line(points[0], points[i]), points[i + 1]) == Enums.TurnType.Colinear)
{
points.RemoveAt(i--);
}
}
if (points.Count <= 3)
{
outPoints.AddRange(points); return(outPoints);
}
Stack <Point> st = new Stack <Point>();
st.PushRange(points.GetRange(0, 3));
for (int i = 3; i < points.Count; ++i)
{
while (HelperMethods.CheckTurn(new Line(st.GetSecondTop(), st.Peek()), points[i])
!= Enums.TurnType.Left)
{
st.Pop();
}
st.Push(points[i]);
}
outPoints.AddRange(st);
outPoints.Reverse();
return(outPoints);
}
public static List <Point> SortPoints(List <Point> points)
{
var(minPoint, idx) = HelperMethods.GetMinPoint(points, 'y');
var minVec = new Vector2D(new Point(minPoint.X + 1234, minPoint.Y));
points.Sort((a, b) =>
{
if (HelperMethods.CheckTurn(new Line(minPoint, a), b) == Enums.TurnType.Colinear)
{
return(Point.GetSqrDistance(a, minPoint).CompareTo(Point.GetSqrDistance(b, minPoint)));
}
return(minVec.AngleTo(new Vector2D(minPoint.VectorTo(a))).Degrees
.CompareTo(minVec.AngleTo(new Vector2D(minPoint.VectorTo(b))).Degrees));
});
return(points);
}
public static bool IsSupportLine(Line l, List <Point> points)
{
int idx = 0;
Enums.TurnType prevSide = Enums.TurnType.Left;//dummy value
bool inside = true;
foreach (Point p in points)
{
if (p.Equals(l.Start) || p.Equals(l.End))
{
continue;
}
var curSide = HelperMethods.CheckTurn(l, p);
if (curSide == Enums.TurnType.Colinear)
{
var dst1 = Point.GetSqrDistance(l.Start, l.End);
var dst2 = Point.GetSqrDistance(l.Start, p);
if (dst1 < dst2)
{
inside = false;
break;
}
}
if (idx != 0)
{
if (curSide != prevSide)
{
inside = false;
break;
}
}
prevSide = curSide;
idx++;
}
return(inside);
}