Fibonacci sequence using array

Question

Going to offer myself for the slaughter here.

Have checked the other questions avail, and can't seem to find the cause of my IndexOutOfRange exception for the following code:

public static int fib2(int n)
    {
        int[] fibarray = new int[n];

        if (n == 0) return 0;

            fibarray[0] = 0;
            fibarray[1] = 1;

            for (int i = 2; i < n; i++)
            {
                fibarray[i] = fibarray[i - 1] + fibarray[i - 2];

            }

            return fibarray[n];

     }

It's something really stupid I'm sure but it's driving me loopy (pun intended)...

tracing this in debug would tell you exactly what the problem is, try with n = 1 — PeskyGnat
– PeskyGnat, Commented Jun 11, 2012 at 12:35

wishper · Accepted Answer · 2012-06-11 12:37:58Z

4

That's the last line!

return fibarray[n];

Your last index in your table is n-1, not n.

Update

And like Attila said, if n=1, the line

fibarray[1] = 1;

will also make a IndexOutOfRange

edited Jun 11, 2012 at 12:37

answered Jun 11, 2012 at 12:32

wishper

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2 Comments

Attila Over a year ago

Also, fibarray[1] = 1; is only valid if n>=2

wishper Over a year ago

Yep indeed, i'll add this. Thanks !

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