I feel that there is no good answer to this. For me It is more about the parts of the solution than the big problems. Some of the big solutions stay but it is mostly how you fit things together that stays with me. Everyone works differently here, e.g. I tend to reuse lots of things other people reimplement them there are drawbacks with both types of learning. I read a lot of code.

Implementing an algorithm like Dancing Links is a hugely rewarding experience as a programmer. You learn by doing.