Computer Science Canada

Recursion Error
Author:  Tewg [ Sun Apr 13, 2008 10:13 pm ]
Post subject:  Recursion Error
I'm having a java.lang.StackOverflowError when i run, i know its n RTP but where would my logic be off, I'm looking to find the lowest number divisable by 1, 20 inclusive.

code:


import hsa.*;
public class Prob5
{
    private static void tryit (int n)
    {
        for (int i = 1 ; i <= 20 ; i++)
        {
            if (n % i != 0)
            {
                tryit (n + 1);
            }
        }
        Stdout.print (n);

    }


    public static void main (String args[])
    {
        tryit (20);
    }
}
Author:  Tewg [ Sun Apr 13, 2008 10:16 pm ]
Post subject:  Re: Recursion Error
ok i tryed it with the smaller numbers 1,10 inclusive which works, but stops 1 number before 2520 (answer) in a continuos loop and i can't for the life of me see why. I have put several output statements in to trace the execution but i still can't find the logic error.
Author:  Tony [ Sun Apr 13, 2008 10:30 pm ]
Post subject:  RE:Recursion Error
Are you sure that recursion is the best method to loop here? The lowest number would be a multiple of all the largest factors (I mean factors that are not already a part of larger factors in the list), so:

11 * 12 * 13 * 14 * 15 * 16 * 17 * 18 * 19 * 20

= 670 442 572 800

That's a lot to stack. Assuming an unreasonably low 1 byte per stack call, you gonna need to find a computer with 670 GB of RAM.

This will probably take a while to run as well.
Author:  Tewg [ Sun Apr 13, 2008 10:33 pm ]
Post subject:  Re: Recursion Error
oh I've already figured this wont work with this bg a number I'm just playing with recursion because i have little to no experience with it.
Author:  Tony [ Sun Apr 13, 2008 10:37 pm ]
Post subject:  Re: Recursion Error
Tewg @ Sun Apr 13, 2008 10:33 pm wrote:
i have little to no experience with it.

It's probably helpful to know how recursion is handled by the compiler/interpreter.
Author:  Tewg [ Sun Apr 13, 2008 10:43 pm ]
Post subject:  RE:Recursion Error
Yah, I'm just reading up on that now, thanks for your help.

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