Better learn as you go, or get a good understanding of the theory before practice?

Trying to work through NC 150, and im wondering whether its better to learn each concept before starting to solve problems, or start the problems, then learn as you go. I'm able to do some easy array, hashmap, linked list and tree problems just on the basis of what ive learned in school, but we havent yet gone into depth about other things and i dont know how to solve problems involving other data structures. also, is it better to completely finish each concept on the NC 150 roadmap before moving to the next, or is it better to simultaneously do problems involving different concepts?