1B has been sight at some point, but not during the entire night.

At least two neighbouring apartments of A toggled lights four or more times during the night, while the occupant of apartment A wasn't consistently in sight that night.

he probably copy pasted the content of this fork and did an edit himself xD

\o/

how about now?

First solver, well done!

Why such a complex solution if the sample space are just 32 bit integers?

This is an old kata, the reference scale for difficulty levels was a bit different back then. Enjoy the cheap ranking points!

O(n) variation aimed at 6 kyu, perhaps 5. Or do you have any other suggestions for interesting variations?

Well, for a code golf, it's in the 7kyu category

Good call. Description was incorrect.

If the next small gift is beyond the specified distance from the current gift, but not further away from your home base than the nearest gift on the opposite side, proceed to collect it.

This is one of those kata's where raising an exception would have been the better option.

Nice one. Do you think an easy variation of this problem could be interesting to have as well on this platform?

Your solution passes all non performance tests now on submit.