What was the point of telling the user what code to write?

Well... coding be hard sometimes.
Actually you probably need O(1) so that means no loops!

I haven't solved it sadly. But given that the inputs are so large, you will need a O(n) solution. So make a spreadsheet of inputs and outputs and look for a pattern: there must be one!

I detrats yb gnidnif eht lacitamehtam .nrettap nehT I desnednoc ti otni eno enil htiw lacigol .srotarepo nehT decalper eht srotarepo htiw esiwtib .seno ehT dne tcudopr si ytelelpmoc elbisneherpmocni

yeah, me too.

One of the best katas on codewars :)

Really satisfying thanks :)
I love a kata where you can simulate it in real life to help!

Worked fine for me :)

I'd also recommend putting any pattern into https://oeis.org/

I'm similar tbf. One trick I use is - if there is just one input - to plot the input and output on a graph. You can then see if there is an obvious solution :)

okay thanks

To that end, is this example in fact not possible?

example 1: Allow citizens of Obristan
example 2: Deny citizens of Kolechia, Republia

Or perhaps it is just the case that the use of this "Deny" is redundant since Kolechia where never allowed in the first place?