public static Poly ConvexHull(Poly poly)
{
Array.Sort(poly.point);
Point adj = new Point(poly.point[0].x, poly.point[0].y);
for (int i = 0; i < poly.point.Length; i++)
{
poly.point[i] -= adj;
}
Array.Sort(poly.point, new PolarPointComparer()); // Vector sort
ArrayList hull = new ArrayList();
for (int i = 0; i < poly.point.Length; i++)
{
Point cur = poly.point[i] + adj;
if (hull.Count > 0 && hull[hull.Count - 1].Equals(cur))
{
continue;
}
while (hull.Count > 1 && Point.Cross((Point)hull[hull.Count - 2], (Point)hull[hull.Count - 1], cur) >= 0)
{
hull.RemoveAt(hull.Count - 1);
}
hull.Add(cur);
}
return(new Poly((Point[])hull.ToArray(typeof(Point))));
}
public void TestConvexHull2()
{
string input = "1,2 4,1 6,1 5,3 3,3 7,3 8,4 6,5 4,5 2,5 3,7 5,6";
string expected = "1,2 2,5 3,7 5,6 8,4 6,1 4,1";
var inputPoly = input.Split(' ').Select(x => new Point(x[0] - '0', x[2] - '0')).ToArray();
var expectedPoly = expected.Split(' ').Select(x => new Point(x[0] - '0', x[2] - '0')).ToArray();
var actual = Poly.ConvexHull(new Poly(inputPoly.ToArray()));
Assert.AreEqual(expectedPoly.Length, actual.point.Length);
for (int i = 0; i < actual.point.Length; i++)
{
Assert.AreEqual(expectedPoly[i], actual.point[i]);
}
}
public void TestConvexHull1()
{
List <Point> al = new List <Point>();
for (int i = 0; i < 5; i++)
{
for (int j = 0; j < 5; j++)
{
al.Add(new Point(i, j));
}
}
Poly p = Poly.ConvexHull(new Poly(al.ToArray()));
Assert.AreEqual(4, p.point.Length);
}
