Programming Job Interview Challenge #4 Answer

So one of the guys over at dev102.com has been posting job interview questions. While the most recent isn't the best interview question in the world, I thought I'd share the answer if anyone is interested.

Here is the question:

How would you implement the following method: Foo(7) = 17 and Foo(17) = 7. Any other input to that method is not defined so you can return anything you want. Just follow those rules:

• Conditional statements (if, switch, …) are not allowed.
• Usage of containers (hash tables, arrays, …) are not allowed.

The answer is crazy simple. Highlight the text below to reveal the answer.

public int Foo(int x)
{
    return -1 * x + 24;
}

My Algebra teacher would be so proud.