How to write recursive function for nested loops in C#

Question

How can I write recursive function for this for loops I am making sum of this array elements.

        int[,,,] exampleArray = new int[1,2,3,4];
        int sum = 0;
        for (int i = 0; i < 1; i++)
        {
            for (int j = 0; j < 2; j++)
            {
                for (int k = 0; k < 3; k++)
                {
                    for (int l = 0; l < 4; l++)
                    {
                        sum += exampleArray[i, j, k, l];
                    }
                }
            }
        }
        Console.WriteLine(sum);

Is this a course question? Seems a very hard one to me. I can't think of a way to write that recursively without increasing the complexity significantly. — PMF
– PMF, Commented Oct 8, 2022 at 18:14
A problem that a data structures teacher at university asked us about — Furkan Şen
– Furkan Şen, Commented Oct 8, 2022 at 18:24

Iłya Bursov · Accepted Answer · 2022-10-08 18:29:47Z

2

it is actually quite simple, just need a way to represent all 4 indexes as single variable:

static int recursiveSum(int[,,,] a, int index = 0)
{
    int ti = index;
    int l = ti % a.GetLength(3); ti /= a.GetLength(3);
    int k = ti % a.GetLength(2); ti /= a.GetLength(2);
    int j = ti % a.GetLength(1); ti /= a.GetLength(1);
    int i = ti % a.GetLength(0); ti /= a.GetLength(0);

    if (ti > 0) {
        return 0;
    }

    return a[i, j, k, l] + recursiveSum(a, index + 1);
}

static void Main(string[] args)
{
    int[,,,] exampleArray = new int[1, 2, 3, 4];
    int sum = recursiveSum(exampleArray);
    Console.WriteLine(sum);
}

answered Oct 8, 2022 at 18:29

Iłya Bursov

24.4k4 gold badges36 silver badges68 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Iłya Bursov Over a year ago

@FurkanŞen start with array where all dimensions are 10, you will notice that indexes will go like 0000, 0001, 0002... ie the normal decimal numbers, then just change base of each digit

Collectives™ on Stack Overflow

How to write recursive function for nested loops in C#

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related