4 replies to this topic

[chili5]

I'm working on this problem where you have a variable n and you want to determine if n! is in a certain range. That is easy but the input data is giving a value for n that is less than zero.

Is there anything that I don't know that says what to do when n < 0?

I learned that factorial was defined recursively as:

f(n) = 1, 0 >= n >= 1
n*f(n-1), n > 1

However, when I implement this I get a wrong answer.

The limit is 10000 - 6227020800. So then n can only be in the range [8,13]. Is there anything I am missing?

Say I get f(-1)? Then what?

[WingedPanther]

Short answer: (-1)! is not defined.
Long answer: look at Math Forum - Ask Dr. Math and Math Forum: Ask Dr. Math FAQ: 0! = 1

Most likely, you're running into an overflow condition.

[chili5]

Thanks. I got it. This problem is wrong then.

When you are given a negative integer that is even, you have to output Underflow, and if it is odd, output Overflow. This is a bad problem. :(

[ZekeDragon]

Is it on the Online Judge?

[chili5]

Yes.

The problem title is "Factorial - You Must Be Kidding me!!!!"

Just realized my title is misleading. :P