I had to scroll down a bazillion solutions to find someone else who bothered to solve in O(log n) time, o(1) space. Good job!

I wonder whether sorting the set and using bisect.bisect_left to find the endpoints of the numbers in [a,b) would pay off? It was only a 7 kyu problem, so I skipped that part.

I thought your code is similar to mine.

Fixed by avermakov

Ruby now has sample tests (added some time ago)

I totally agree with OP. The description sucks. Guessing your way out of a bad description does not count as a special required skill on the part of the solver, but of an obnoxious attitude of the author.

I solved in Ruby, which is where the broken test case is, but the "guessed degrees" part applies to all languages.

Can you specify which language this occurs in please?

The restrictins in Python are ridiculous and don't allow for much variety in or elegant solutions.