Most beneficial CodingBat problems for AP CS A FRQs I love the CodingBat platform and plan to integrate it throughout my course next year. Yet, since it will be my first year with AP CS A and I have not yet had a chance to study past years' FRQs, I'm not sure which sections I should focus on more than others. 

Based on your experience, what sections of CodingBat are most helpful in terms of preparing students for the FRQs on the AP Exam?

(Note: I am asking about the problems already on the site, not ones I could author myself -- that's a separate topic as I see it.)
They've got an AP-1 category which is based on past FRQs. Not the whole question, but pieces. I'd make sure you hit every one in that category during the year. The String-2 and Array-2 are also good. 

I use CodingBat and similar questions as warm-ups all year long. We start pretty much as soon as students are able to fill in a method. 

Pretty much anything that involves looping through strings or arrays will help them with the test in May. Usually 2 or 3 of the FRQs involve iterating through some type of list structure and doing something with the values. I try to get my students to a point where they really don't have to think about loops, they just type on when they need it.