E. Lagged Speed
Author: Alham Fikri Aji
Prepared By: Alham Fikri Aji, Suhendry Effendy
(link to problem E)
I don’t like this problem. I didn’t mean it’s not a good problem, but I hate it because this problem made me stress 😛
You can solve this problem in two ways: by observing the values, or by finding the pattern. I solved this problem using the former method. With the help of drawing tool (I used gnuplot), I observed that there are two line shapes made by the speed changes (S), i.e. (1) increasing head, and (2) bouncing and converging tail. From there, I “only” need to derived the formula for those two shapes. However, this “only” task took me 1 hour. Another approach is by finding the pattern. As I don’t like this approach, I didn’t use it. But some contestants said that this appraoch is much easier. I also noticed that most of the accepted submissions used this approach – one line formula.
There are 156 submissions have been made for this problem, in which 12 teams managed to get accepted. The first team who solve this problem is GantengGantengKoder (minute 164) from Institut Teknologi Bandung.