Talk:Special factorials
Reverse factorial algorithm
I took a stab at translating the reverse factorial algorithm used in the Factor entry to Java. It should be almost as efficient as taking the factorial itself. <lang java>public static int rf(int n) {
int a = 1;
int b = 1;
while (n > a) {
b++;
a = a * b;
}
if (a == n)
return b;
else return -1; //undefined
}</lang>