I don't think so.

I'm not sure of that, but probably singleWhere will always tranverse the whole list to ensure the condition was just met once.

Given we know that only and just one number will be a outlier, using firstWhere is better than singleWhere.

The use of singleWhere is brilliant! Why write new logic when the language already provides it :)

it doesn't work on dart.
i tried my solution on pc and dart pad - all works perfectly.
but here it fail tests every time.
maybe it is something to o with dart vesions(here is 2.1 and dart is already 2.7), i dunno.

and it's not 6 kyu kata. it's atleast 5.

you are a man of Italian culture.
Cool solution.

this is fun solution, but pretty heavy to read.
you clearly a man.