Factorial n!

Computing n!

There are many ways to compute n!, but I will introduce a divide and conquer method.
Using these rules below:
f(n,m) = 1 if n == m,
f(n,m) = 0 if n > m,
f(n,m) = f(n,x) * f(x+1,m) where x = (n + m)/2, otherwise

int f(int n, int m)
{
   if ( !(n < m) ) return n == m;
   int x = (n + m) / 2
   return f(n,x) * f(x+1,m);   
}