Didn't have to be so specific for this one, compare with mine.

Nice ternary though! 😎

I assume you mean [a-zA-Z] and yes that's required to match upper case letters after the symbols.

From experience it feels like a 4/5kyu.

Your comment helped me, I wondered why it didn't work for 20 and came to read the comments to see if there was a problem with the test cases, but no it was my own code. Rounding errors on rows 11 and 15.

Take a look at row 11 ([1, 11, …, 11, 1]). Compare it to what your outputs.

Be careful with floating points!

Depends on the language I guess, but yeah probably.

Took me a while looking through the Array docs to find product, I was trying hacky ways with permutation before that.

This code is better than my own though!

Gaming the system!

I used [a-z] in mine as you don't want to .upcase on non-letters.

The letter after the underscore/hyphen matched in the regex.

There are brackets around the full stop, those brackets are what you can reference with $1 and so on.

Annoyingly I did it this way but the timeout's come down since then so it failed!