private static void solve(List <Point> points, Hull hull, List <Triad> triads, bool hullOnly)
{
int N = points.Count;
double[] distSqCentre = new double[N];
int[] sortedInd = new int[N];
for (int i = 0; i < N; i++)
{
distSqCentre[i] = points[0].distSqTo(points[i]);
sortedInd[i] = i;
}
Array.Sort(distSqCentre, sortedInd);
int mid = -1;
double rmin2 = double.PositiveInfinity, circumcentreX = 0, circumcentreY = 0;
Triad tri = new Triad(sortedInd[0], sortedInd[1], sortedInd[2]);
for (int i = 2; i < N; i++)
{
tri.c = sortedInd[i];
if (tri.findCircumcircle(points) && tri.circumcircleR2 < rmin2)
{
mid = i;
rmin2 = tri.circumcircleR2;
circumcentreX = tri.circumcircleX;
circumcentreY = tri.circumcircleY;
}
else if (rmin2 * 4 < distSqCentre[i])
{
break;
}
}
if (mid != 2)
{
int midInd = sortedInd[mid];
double distSqMid = distSqCentre[mid];
Array.Copy(sortedInd, 2, sortedInd, 3, mid - 2);
Array.Copy(distSqCentre, 2, distSqCentre, 3, mid - 2);
sortedInd[2] = midInd;
distSqCentre[2] = distSqMid;
}
tri.c = sortedInd[2];
tri.makeClockwise(points);
tri.findCircumcircle(points);
triads.Add(tri);
hull.Add(new HullPoint(points, tri.a));
hull.Add(new HullPoint(points, tri.b));
hull.Add(new HullPoint(points, tri.c));
Point centre = new Point(circumcentreX, circumcentreY);
for (int i = 3; i < N; i++)
{
distSqCentre[i] = points[sortedInd[i]].distSqTo(centre);
}
Array.Sort(distSqCentre, sortedInd, 3, N - 3);
int T = 0;
for (int i = 3; i < N; i++)
{
int pInd = sortedInd[i];
HullPoint p = new HullPoint(points, pInd);
double dx = p.x - hull[0].x, dy = p.y - hull[0].y;
int H = hull.Count, hInd = 0;
List <int> pInds = new List <int>(), tInds = new List <int>();
if (hull.edgeVisibleFrom(0, dx, dy))
{
hInd = 0;
if (hull.edgeVisibleFrom(H - 1, dx, dy))
{
pInds.Add(hull[H - 1].pInd);
tInds.Add(hull[H - 1].tInd);
for (int h = 0; h < H - 1; h++)
{
pInds.Add(hull[h].pInd);
tInds.Add(hull[h].tInd);
if (hull.edgeVisibleFrom(h, p))
{
hull.RemoveAt(h);
h--;
H--;
}
else
{
hull.Insert(0, p);
H++;
break;
}
}
for (int h = H - 2; h > 0; h--)
{
if (hull.edgeVisibleFrom(h, p))
{
pInds.Insert(0, hull[h].pInd);
tInds.Insert(0, hull[h].tInd);
hull.RemoveAt(h + 1);
}
else
{
break;
}
}
}
else
{
hInd = 1;
pInds.Add(hull[0].pInd);
tInds.Add(hull[0].tInd);
for (int h = 1; h < H; h++)
{
pInds.Add(hull[h].pInd);
tInds.Add(hull[h].tInd);
if (hull.edgeVisibleFrom(h, p))
{
hull.RemoveAt(h);
h--;
H--;
}
else
{
hull.Insert(h, p);
break;
}
}
}
}
else
{
int e1 = -1, e2 = H;
for (int h = 1; h < H; h++)
{
if (hull.edgeVisibleFrom(h, p))
{
if (e1 < 0)
{
e1 = h;
}
}
else
{
if (e1 > 0)
{
e2 = h;
break;
}
}
}
if (e2 < H)
{
for (int e = e1; e <= e2; e++)
{
pInds.Add(hull[e].pInd);
tInds.Add(hull[e].tInd);
}
}
else
{
for (int e = e1; e < e2; e++)
{
pInds.Add(hull[e].pInd);
tInds.Add(hull[e].tInd);
}
pInds.Add(hull[0].pInd);
}
if (e1 < e2 - 1)
{
hull.RemoveRange(e1 + 1, e2 - e1 - 1);
}
hull.Insert(e1 + 1, p);
hInd = e1 + 1;
}
if (hullOnly)
{
continue;
}
int a = pInd, T0;
int P = pInds.Count();
T = T0 = triads.Count();
for (int j = 0; j < P - 1; j++)
{
Triad t = new Triad(a, pInds[j], pInds[j + 1]);
t.findCircumcircle(points);
t.bc = tInds[j];
if (j > 0)
{
t.ab = T - 1;
}
t.ac = T + 1;
Triad u = triads[tInds[j]];
if ((t.b == u.a && t.c == u.b) || (t.b == u.b && t.c == u.a))
{
u.ab = T;
}
else if ((t.b == u.a && t.c == u.c) || (t.b == u.c && t.c == u.a))
{
u.ac = T;
}
else if ((t.b == u.b && t.c == u.c) || (t.b == u.c && t.c == u.b))
{
u.bc = T;
}
triads.Add(t);
T++;
}
triads[T - 1].ac = -1;
hull[hInd].tInd = T - 1;
if (hInd > 0)
{
hull[hInd - 1].tInd = T0;
}
else
{
H = hull.Count;
hull[hull.Count - 1].tInd = T0;
}
}
}
