not a good practice as we are splitting the string and indexing it at each iteration while it can be done only once

Yeah could have simplified even more like that, to me kata 7 you could make it straightforward and easy to read. If you interested on golf solution, yes, we could use this or even better came out with an equation for the number lines.

Anyways, thanks for the note, Hope keep it here for future reference.

Oh no worries, it just didn't update but now its invalid.

Sorry for coming with a native method for a performance tag problem. I am just trying it at first and it works; As a saying "If it works, Don't Touch It!".

Anyways, Sorry for the inconvenience.

Thought I invalidated this solution with large tests (just added more tests and when I tested this, it said TLE). So, is it supposed to be an invalid solution?

a class var would be better, yes.

Lol, I'm really thought that the a.extend(b) as a requirement on this kata. I Think I Overthink Things.

@FArekkusu comments help me alot! Thanks!