Question

I have a simple recursive algorithm, which returns Fibonacci numbers:

private static double fib_recursive(int n){
    if(n <= 2) return 1;
    else return fib_recursive(n-1) + fib_recursive(n-2);
}

Now my task is to return the time, which this method would take to calculate the 400-th fibonacci number on a given computer e.g. fib_recursive(400). “Would” is in bold, because I can’t run the function, as it would take to long for this method to give an answer.

How can it be best achieved?

Answer 1

Calculate how much time to do each recursive call, figure out how many recursive calls, and you have an answer.

There are faster ways to do this, using a smarter recursion algorithm, but for your algorithm just put in some timing information.