Hi.

Can someone give me tips on how to solve problem I from NWERC 2009?

I've tried to solve it using something like a merge of many convex hulls but, besides being too complicated, the time complexity of this approach is quite high.

Any help is appreciated. Thanks!

There are maybe a lot of techniques to create the polygon. One that came to my mind is to create a lower hull, and then add the other points in the top part of the polygon sorted by x coordinate, and the tie breaker is y coordinate.

I was looking into the same problem and your solution works, got AC.

Thanks man!!