How recursive algorithm work in this case? And what type of recursion is ?

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C#

public void Recursion(int position)
        {
            itemLevel++;
            permutation.SetValue(itemLevel, position);
            if(itemLevel == numOfItems)
            {
                AddPermutation(permutation);
            }
            else
            {
                for(int currentPosition = 0; currentPosition < numOfItems;
                    currentPosition++)
                {
                    if(permutation[currentPosition] == 0)
                    {
                        Recursion(currentPosition);
                    }
                }
            }
            itemLevel--;
            permutation.SetValue(0, position);
        }

Posted 11-Sep-13 10:16am

venetaNimani

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Richard C Bishop 11-Sep-13 16:17pm

It works by running the same method within itself. It could be used to get a sub-set of data out of a larger set, etc.

Sergey Alexandrovich Kryukov 11-Sep-13 17:04pm

This "withing" sounds pretty inaccurate. Recursion does not modify the scope of execution. All run-time nesting is possible because the stack frame lies on the stack...
—SA

Richard C Bishop 11-Sep-13 17:07pm

Fair enough. Can you suggest a better way I could describe it please?

Sergey Alexandrovich Kryukov 11-Sep-13 17:11pm

Well, I'm going to give OP a reference to the Wikipedia article "recursion", but, for deep understanding, it would be the best to reference one of the numerous textbooks where it is explained how stack works with call/return instruction. I think each developer should also learn how it works in a CPU...
—SA

Sergey Alexandrovich Kryukov 11-Sep-13 17:16pm

I added some references, please see.
—SA

Sergey Alexandrovich Kryukov 11-Sep-13 17:03pm

It would be useful for you just to run it step-by-step under the debugger and see how recursion works. Why asking? And I think talking of "type of recursion" is just science-like blah-bladology. :-)
Is at a school/interview test question or a homework?
—SA

joshrduncan2012 11-Sep-13 17:13pm

Good nose! :) I smelled something related to school, too.

Sergey Alexandrovich Kryukov 11-Sep-13 17:17pm

:-)

venetaNimani 11-Sep-13 20:38pm

It's homework

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Sergey Alexandrovich Kryukov · Answer 1 · 2013-09-11T11:16:00

Please see the comments to the question.

Please see:
http://en.wikipedia.org/wiki/Recursion[^],
http://en.wikipedia.org/wiki/Recursion_%28computer_science%29[^],
http://en.wikipedia.org/wiki/Stack_%28abstract_data_type%29[^] (this is not what is used in recursion, but good to know, too),
http://en.wikipedia.org/wiki/Call_stack[^] (but that is it).

I think this explanation is deep enough: http://www.cs.umd.edu/class/sum2003/cmsc311/Notes/Mips/stack.html[^].

Good luck,

—SA