You should avoid at all cost switch/case statements, its a case smell.

This solution and others like it has helped me a lot with refactoring

Thanks for the tip. I think the Kata description has changed since I wrote my solution.

Nice regex, but the type checking is wrong. The statement says "If n is not an integer, return an empty value."
Try using #instance_of? or #is_a? instead of a "truthy" test.

That is an extra fail-safe. In the chance that strarr.each_cons(k).map(&:join).max_by(&:length) returns nil, which it will if the array strarr is empty, then an empty string will be returned. Since nil is falsey, '' (the empty string) will be returned when the || expression is evaluated on the last line—since strings are considered truthy. The first line of the method should handle cases where strarr points to an empty string, but it's not bad to have a back up.

Thank you for this comment rsrs. I started to study this year and I was looking and wondering why people were converting to strings and than back to integer

what if the sequence 'step' isn't one? what if it's increasing by 2 for example?

Matches any substrings of consecutive non space characters. See here for example.

Could you explain to me what the "\ S +" does?

If the resulting array is empty, calling first will yield nil, which needs to be converted into 0. This can be done either by using to_i or || 0.

Why would .to_i be necessary? The array consists of integers only.

Well done.

what is the purpose of || "" at the end?

Each time its 5 times less code than mine :D

Okay Gauss