Depends on why it took 15 hours to figure out the problem and make it work. I would presume he (you) learned something during the process, so if it had to be repeated you wouldn't have the same false starts and understand the general solution much quicker. After that, comments should help the coder understand the details like edge cases and non-obvious decisions.
I speak from a recent similar experience where I had to build a fairly complex piece of multi-threaded image processing code on Android. Starting out there was a lot of knowledge about image processing and Android that I simply did not know. Learning and internalizing that information took a significant chunk of time reading the docs and other peoples code. Only then could I fully understand my particular problem and implement a solution.
Depends on why it took 15 hours to figure out the problem and make it work. I would presume he (you) learned something during the process, so if it had to be repeated you wouldn't have the same false starts and understand the general solution much quicker. After that, comments should help the coder understand the details like edge cases and non-obvious decisions.
I speak from a recent similar experience where I had to build a fairly complex piece of multi-threaded image processing code on Android. Starting out there was a lot of knowledge about image processing and Android that I simply did not know. Learning and internalizing that information took a significant chunk of time reading the docs and other peoples code. Only then could I fully understand my particular problem and implement a solution.