Given the runtime of an algorithm to be m!/(n!*(m-n)!) That is mCn, where both m and n are variables, is the complexity factorial or polynomial? Or is it something else?

Please elaborate.



The growths could be linear or constant depending on the relationship between $m$ and $n$ as they grow large. For example, if $n$ grows with $m$ as in $m=n+1$, then $\binom{m}{n}=\binom{n+1}{n}=n+1$.

Now, if you are interested in the maximum growth, then the binomial coefficients $\binom{m}{n}$ are largest when $n$ is half of $m$. Put $m=2n$ and use Stirling's approximation for the factorial. You get

$$\binom{2n}{n}=\frac{(2n)!}{(n!)^2}\sim \frac{(2n)^{2n}e^{-2n}\sqrt{4n\pi}}{n^{2n}e^{-2n}2n\pi}=\pi^{-1/2}2^{2n}n^{-1/2}$$


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.