三、(15%) You are required to compute the binomial coefficient $$Ck^n = \frac{n!}{k!(n-k)!}$$. When n or k is not small, we cannot compute $$Ck^n$$ directly from the definition because n! or k! is very large. Please design an algorithm to compute $$C_k^n$$ in time O(nk) without computing n! or k! directly.