My solution was very similar :')

Simple, fast and readable.
Best solution!

This solution is very readable but a bit slow/expensive.

You could turn all of the string to lowercase just once, instead of twice (imagine a VERY long string, it would make a big difference)
Splitting also means going through the whole string twice.

A more efficient way of solving this is to transform text to lowercase once, then work only with one array.

I did the same thing, but maybe it's a bit more readable :')
I think it's one of the best ways to solve this

This is a lot of code... You can use math or use something similar to my solution as well