If you're getting a CS degree and wanting to pursue a BSN, get your prerequisites done for the BSN while completing your CS stuff. If you're looking to double-major, complete all but a very few courses in your CS program so that when you get going in your BSN program, you can take those courses, and time everything out right so that when you finish your BSN program, you get your CS degree too. Your other option is to get your CS degree and right at the tail end of it, start an ABSN as you (hopefully) should have all the stuff for that all done to allow you entry.
I have a BS degree already. If an ABSN program was a viable option for me, I would have taken it. Given how much information is thrown at you, I would generally discourage trying to double-major anything with Nursing unless you can somehow figure a way to finish both degrees at the same time while essentially doing them serially.