Change combinations to for comprehension. It runs 0.8xS for worst cases. It may run faster if I don't use BigInt and handcraft a bitCount method. But I don't think it's worthy.
Change combinations to for comprehension. It runs 0.8xS for worst cases. It
may run faster if I don't use BigInt and handcraft a bitCount method. But I
don't think it's worthy.

advancedxy/hackerrank,advancedxy/hackerrank,advancedxy/hackerrank