nice solution! I also wonder about a more detailed explanation about the i<=n/k condition. I realize it is definitely correct and it is to save us from producing duplicate combo that are only different in order. And it is also easy to see that when k=2. but when k>2, I'm having some trouble wrapping my head around it. thanks a lot!
Alright, rephrasing it to "'null' or 'invalid' or 'not possible' in the context of the application of the problem"
The application of the problem (for solving a puzzle) did not require the k = 0 and n = 0 case because that case simply does not exist for the puzzle. I did not include k = 0 and n = 0 test case in the OJ on purpose, while setting the problem.
I agree with you on the fact the solution gets simple if you start looking at things from the base case.