Ruby translation

Ruby translation

This expression represents the physical meaning of the first derivative.
See omegahm's explanation (first best solution)

I forgot to do it, thanks

I rewrote my solution

I'm just learning, but it seems to me that my last solution has O (1) complexity. Or am I wrong ?

I agree with you. Now I have more practice, and I would rewrite my solution with || operator, shorter version of .map{|j| j.to_i} and so on

Because 2 is a prime