How to politely say no?

I have recently participated in an online code competition held in my college. Whole CSE branch from all the batch participated but only I was able to complete the problem in the given time. Now people are pesting me to tell my code. The problem is If I tell them my code then they might participate in the competition again with a different account. And I don't want that to happen. This information spread like a fire and now more and more people are pesting me. I have to turn them down without sounding mean. Please help?