The company has asked for assignment submission. The was well thought through to have enough complexities, and will take your weekend easily. The problem here is even if you have give general solution to solve the puzzle they still want to see your exact solution along with junits. So you have to do definitely put more effort. Sometimes they may ask to change the design for their convenience. But the worst case thing happen to me is they dont even care after submitting the assignment even though you follow them up with reminders. I would suggest don't spend much of your time here, they can be easily unrecognised.