simply cuz 1+1=2
but 97+97!=98

Same lol

Nice, but mine is better :P

Could've also used 1 in the place of 0 if im not mistaken...

Only a tip, the "if" is not necessary because the rangeClosed returns only one number when both are equals, and the sum() returns the number. Just a tip, but it was a clever answer, nice job!!!

me too hahaha

Relatable haha

after my 50 line solution i feel so stupid lol

Boxing to Character is unnecessary in this case. Both methods toUpperCase / toLowerCase have overloaded versions that accept a codepoint.

In general, it's not a good practice to reassign the method argument.
If you are curious why - then please look at these method signatures.
It's a pretty helpful example because Node arguments have a meaningful name (and in general they must be meaningful).
And then if we treat an argument head as a usual variable its name becomes pointless.
And moreover in the case, if a method is much larger than a few lines or has an intricate logic then it's easy to introduce a bug because you forget that 'head' no longer points to the head.

sorry, what do (?=[\w\d{}\[\]]+$) mean?

And what if s3 is a bazillion?

It does not seem particularly efficient to range over 1..bazillion in steps of 1 looking for multiples