/// <summary>
/// The Graham Scan algorithm determines the points belonging to the convex hull in O(n lg n).
/// </summary>
/// <param name="points">set of points</param>
/// <returns>points in the convex hull</returns>
/// <seealso href="http://en.wikipedia.org/wiki/Graham_scan">Graham scan, Wikipedia</seealso>
public static List <Point> GrahamScan(List <Point> points)
{
if (points.Count <= 3)
{
return(new List <Point>(points));
}
var ps = new List <Point>(points);
ps.Sort(new CompareYThenX());
ps.Sort(new PolarComparator(ps[0]));
Deque <Point> hull = new ArrayDeque <Point>();
hull.Push(ps[0]);
hull.Push(ps[1]);
hull.Push(ps[2]);
for (int i = 3; i < points.Count; i++)
{
var top = hull.Pop();
while (hull.Any() && !IsLeftTurn(hull.Peek(), top, ps[i]))
{
top = hull.Pop();
}
hull.Push(top);
hull.Push(ps[i]);
}
return(new List <Point>(hull));
}
/// <summary>
/// Returns the next Event or {@code null} if there are no more events or
/// the walker is closed.
/// </summary>
internal virtual Event Next()
{
DirectoryNode top = Stack.Peek();
if (top == null)
{
return(null); // stack is empty, we are done
}
// continue iteration of the directory at the top of the stack
Event ev;
do
{
Path entry = null;
IOException ioe = null;
// get next entry in the directory
if (!top.Skipped())
{
IEnumerator <Path> iterator = top.Iterator();
try
{
//JAVA TO C# CONVERTER TODO TASK: Java iterators are only converted within the context of 'while' and 'for' loops:
if (iterator.hasNext())
{
//JAVA TO C# CONVERTER TODO TASK: Java iterators are only converted within the context of 'while' and 'for' loops:
entry = iterator.next();
}
}
catch (DirectoryIteratorException x)
{
ioe = x.InnerException;
}
}
// no next entry so close and pop directory, creating corresponding event
if (entry == null)
{
try
{
top.Stream().Close();
}
catch (IOException e)
{
if (ioe != null)
{
ioe = e;
}
else
{
ioe.AddSuppressed(e);
}
}
Stack.Pop();
return(new Event(EventType.END_DIRECTORY, top.Directory(), ioe));
}
// visit the entry
ev = Visit(entry, true, true); // canUseCached - ignoreSecurityException
} while (ev == null);
return(ev);
}
