How to compute log(N!) WITHOUT using recursion?

[dullboy]

Thanks for your inputs!

[wildfrog]

Maybe this page can give you some tips:
http://mathworld.wolfram.com/Factorial.html

- petter

[Pinky98]

Just use a loop...

e.g. in M$ C,

__int64 g = 1;
for (int i=1; i<=N; i++)
{
g = g * i;
}
return log(g);

Your big problem is trying to get a type large enough to contain your factorial.

[D_Drmmr]

log(n!) = log(n*(n-1)*...*2*1) = SUM(i = 1, ..., n; log(i))
So you can do this:

double sum = 0.;
for (int i = n; i > 0; --i)
sum += log(i);

Which will solve the overflow problem.

[bilm_ks]

D_Drmmr is right although you pay the cost (speed).