Thx :)

It's lambda-function, which finds out is number even (return true) or not (return false).

simple as that, well done :)

Random tests are wrong, there are several rows with the same product_id and date. But description says "Only one transaction for a product_id per date is possible."

I agree that this is cheating even though I have the same solution.LOL

An amazing solution. It's a pity that I won't be able to do this for a long time . . .

Is this mathematically correct ? I don't think it will work for all integers..

beautiful and cool solution

noice

no way

size_t is already the type used in the current version of the kata. We were talking about using another type since size_t is for particular uses and is not suited here.

Hehe newbie problems... Made "size_t" version https://www.codewars.com/kumite/62f45878bd09cd0030ee4513?sel=63021bd8acfb8d000e5b4cfa