There is a lot of wrong information on this board - most likely posted by ignorant high school / undergrad students who clearly don't know jack. One piece of wrong information that keeps popping up is that computer science is massively helpful for sales and trading (S&T) at a BB. Wanna know the truth?
YOU DO NOT NEED ANY CS FOR BB S&T
Unless you specifically want the exotics desk, the only programming language you ever need to know for BB S&T is VBA for Excel, nothing more. And you do not need to know about data structures or algorithms to learn this language - it should be dirt easy. So please don't major in CS just for the sake of BB S&T recruiting. At best it will give you a marginal advantage (and you will use little to none of Java/C++ on the job) and at worst, it will fuck up your GPA.
Unless you want quant (algorithmic) trading, stick to Econ and basic finance, sprinkled with some probability/stats courses. Oh and a high GPA won't hurt either..
Hope this clears up some confusion.