App Academy is all about algorithmic aptitude. For their application I did all the practice problems and a ton of Code Wars. Doing those problems is hard but it becomes easier with practice. My goal has been to master the more difficult problems under 15 minutes. Its a drill that takes a long time because there are so many problems to cover.
An update on Hack Reactor. I had a great experience interviewing with Hack Reactor. Such a nice interviewer and it was a both educational and fun. I got in!! This is great! I am feeling good. Hack Reactor check.