I’m not too good with java, but it should be something like this:

public static int convertRomanNumeral(string n){Map.of("M","DD","CD","CCCC","D","CCCCC","C","LL","XL","XXXX","L","XXXXX","X","VV","IV","IIII","V","IIIII");.forEach((k,v)->{n=n.replace(k,v);});return n.length();}

Since Roman numerals have an upper bound, the time complexity is always O(1).

It’s besically android without the Google parts.

I just bought the Fairphone 6 with /e/os. I am pleasantly surprised with how many apps work just fine.