public void CopyInto(IPosition[] vals, int i)
{
CDLL node = this;
do
{
vals[i++] = node.val; // still, implicit checkcasts at runtime
node = node.next;
} while (node != this);
}
public void PrintFwd()
{
CDLL node = this;
do
{
Console.WriteLine(node.val);
node = node.next;
} while (node != this);
Console.WriteLine();
}
public int Size()
{
int count = 0;
CDLL node = this;
do
{
count++;
node = node.next;
} while (node != this);
return(count);
}
/*
* public SimplePositionSet ConvexHull(SimplePositionSet ps)
* {
* int n = ps.GetCount();
* Point[] pts = new Point[n];
* for (int i = 0; i < n; i++)
* {
* SimplePosition pos = ps.GetNextPosition();
* pts[i] = new Point(pos.GetX(), pos.GetY());
* }
* Point[] resPts = _ConvexHull(pts);
* SimplePositionSet result = new SimplePositionSet();
* for (int i = 0; i < resPts.Length; i++)
* result.AddPosition(new SimplePosition(resPts[i].X, resPts[i].Y));
* return result;
* }
*/
public IPositionSet ConvexHull(IPositionSet ps)
{
//转换成数组
IPosition[] posArr = (IPosition[])ps.ToArray();
int N = posArr.Length;
//排序
Polysort.Quicksort(posArr);
IPosition left = posArr[0];
IPosition right = posArr[N - 1];
// Partition into lower hull and upper hull
CDLL lower = new CDLL(left), upper = new CDLL(left);
for (int i = 0; i < N; i++)
{
double det = Area2(left, right, posArr[i]);
if (det > 0)
{
upper = upper.Append(new CDLL(posArr[i]));
}
else if (det < 0)
{
lower = lower.Prepend(new CDLL(posArr[i]));
}
}
lower = lower.Prepend(new CDLL(right));
upper = upper.Append(new CDLL(right)).Next;
// Eliminate points not on the hull
eliminate(lower);
eliminate(upper);
// Eliminate duplicate endpoints 消除重复点
/*
* if (lower.Prev.val.Equals(upper.val))
* lower.Prev.Delete();
* if (upper.Prev.val.Equals(lower.val))
* upper.Prev.Delete();
* */
// Join the lower and upper hull
IPosition[] res = new IPosition[lower.Size() + upper.Size()];
lower.CopyInto(res, 0);
upper.CopyInto(res, lower.Size());
PositionSetEdit_ImplementByICollectionTemplate result = new PositionSetEdit_ImplementByICollectionTemplate();
for (int i = 0; i < res.Length - 1; i++)
{
result.AddPosition(res[i]);
}
return(result);
}
// Graham's scan
private void eliminate(CDLL start)
{
CDLL v = start, w = start.Prev;
bool fwd = false;
while (v.Next != start || !fwd)
{
if (v.Next == w)
{
fwd = true;
}
if (Area2(v.val, v.Next.val, v.Next.Next.val) < 0) // right turn
{
v = v.Next;
}
else
{ // left turn or straight
v.Next.Delete();
v = v.Prev;
}
}
}
public CDLL Append(CDLL elt)
{
elt.prev = this; elt.next = next; next.prev = elt; next = elt;
return(elt);
}
public CDLL Prepend(CDLL elt)
{
elt.next = this; elt.prev = prev; prev.next = elt; prev = elt;
return(elt);
}
// Delete: adjust the remaining elements, make this one Position nowhere
public void Delete()
{
next.prev = prev; prev.next = next;
next = prev = null;
}
// A new CDLL node is a one-element circular list
public CDLL(IPosition val)
{
this.val = val; next = prev = this;
}
