To be fair, the Supreme Court's standard is pretty confusing!
As to your example, I suspect he answer is still "no." It's not enough to just "add something" to the abstract idea--the thing you add has to have an "inventive concept." Field of use limitations ("quicksort to sort birthdays") or post-solution activity ("quicksort then you do something else") do not make the abstract idea patentable. Routine activity--and arguably, adapting algorithms to different data formats is routine in programming--aren't sufficient either.
One thing that's left unsaid in the cases but that matters in practice is that the patent has to "seem like a real invention" that produces a useful result. Courts deny that they do this, but post-Alice there has been a tendency to inject elements of obviousness and novelty into the issue of patentability. If your algorithm doesn't seem like it was hard to come up with, or it just produces numbers that are not directly useful to the end user, it's going to get labeled "abstract idea."
E.g. consider an algorithm for distributed reference counting. That'll get dinged as an abstract idea. However, if you come up with a way to manage image/video resources in a distributed cache that happens to use a distributed reference counting algorithm, that might pass muster.
Finally, the law has changed a lot in the last 6-7 years. But there are still lots of patents out there from back when the law was laxer that are getting litigated (and often invalidated in light of Alice).
