Reverse factorial

Question

Well, we all know that if N is given it\'s easy to calculate N!. But what about the inverse?

N! is given and you are about to find N - Is that possible ? I\'m curio

Answer 1

int p = 1,i;
//assume variable fact_n has the value n!
for(i = 2; p <= fact_n; i++) p = p*i;
//i is the number you are looking for if p == fact_n else fact_n is not a factorial

I know it isn't a pseudocode, but it's pretty easy to understand