# Why is Sklansky algorithm convex hull wrong

I stumbled across this incorrect O(n) algorithm for calculating convex hulls by Sklansky, but it was later proved to be wrong.

My problem is this: why is it wrong? What is an example polygon that could give this error? Who figured it out to be wrong, and is there a paper showing it is wrong? (or does anyone have the example used to show it's wrong)

Thanks

• A. Bykat, Convex hull of a finite set of points in two dimensions, pp. 296-298. – Cave Johnson Feb 2 '18 at 13:16
• I can't find a copy of that paper – code base 5000 Feb 2 '18 at 13:34
• There were two algorithms by Slansky, both incorrect. Which one do you mean? – Professor Vector Feb 2 '18 at 13:56
• The first page of Bykat's paper is freely available at doi.org/10.1016/0020-0190(78)90021-2 – lhf Feb 2 '18 at 14:38

void convexHull(InputArray points, OutputArray hull, bool clockwise=false, bool returnPoints=true )

Note also that the complexity of Sklansky's Convex Hull algorithm is $$O(N\log N)$$.