Converting 3D-Array to List in C#

Question

For easily finding values in a huge Array I want to use the "find"-Command of a List. The problem is, right now it is not a List, it is a 3D-Array.

This means, i need to convert my double[,,]-array to a

List<List<List<double>>> blabla

Example of an Array:

double[,,] myArray = new double[2,3,3];

Could look then like the following:

myArray[1,:,:] =  1.11 1.12 1.13
                  1.21 1.22 1.23
                  1.31 1.32 1.33

myArray[2,:,:] =  2.11 2.12 2.13
                  2.21 2.22 2.23
                  2.31 2.32 2.33

Can this be done by a one-liner using somehow the "Cast" command?

Thanks

Multidimensional arrays have very few uses outside pure maths, what are you trying to accomplish? — Mitch
– Mitch, Commented Sep 1, 2014 at 2:13
It will be really hard, if possible at all, to get a one-liner without creating your own method and calling it, but I don't think that's what you meant — MarcinJuraszek
– MarcinJuraszek, Commented Sep 1, 2014 at 2:21
@Mitch Actually I use it for an optimization algorithm, which is quite math-based. But I often have to find some values or check whole rows of this array, which is much more easy using a List. But if there is no easy conversion possibility, I will probably change from multidimensional array to a List :) Thanks for the help — Krus
– Krus, Commented Sep 1, 2014 at 2:36
@MarcinJuraszek - Challenge accepted! Please see my "one-liner" answer. ;-) — Enigmativity
– Enigmativity, Commented Sep 1, 2014 at 4:01

Enigmativity · Accepted Answer · 2014-09-01 03:46:09Z

1

Given your double[,,] myArray you can do this:

var blabla = 
    myArray
        .Cast<double>()
        .Select((v, n) => new
        {
            x = n / (myArray.GetLength(2) * myArray.GetLength(1)),
            y = (n / myArray.GetLength(2)) % myArray.GetLength(1),
            value = v,
        })
        .GroupBy(q => q.x)
        .Select(q =>
            q
                .GroupBy(
                    w => w.y,
                    w => w.value)
                .Select(e => e.ToList())
                .ToList())
        .ToList();

That gives you the List<List<List<Double>>> that you're looking for.

And all in a one-liner!

answered Sep 1, 2014 at 3:46

Enigmativity

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Comments

Seminda · Accepted Answer · 2014-09-01 02:51:14Z

you can do it. you have to loop the items and get the result. check the sample code

double[, ,] array3D = new double[2, 3, 3] { { { 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 } }, { { 10, 11, 12 }, { 13, 14, 15 }, { 16, 17, 18 } } };


        List<List<List<double>>> topLevel = new List<List<List<double>>>();

        for (int a = 0; a < array3D.GetLength(0); a++)
        {
            List<List<double>> secondLevel = new List<List<double>>();
            for (int b = 0; b < array3D.GetLength(1); b++)
            {
                List<double> thirdLevel = new List<double>();
                for (int c = 0; c < array3D.GetLength(2); c++)
                {
                    thirdLevel.Add(array3D[a, b, c]);
                }
                secondLevel.Add(thirdLevel);
            }
            topLevel.Add(secondLevel);
        }

Output: enter image description here

Mitch · Accepted Answer · 2014-09-01 03:11:18Z

0

Not quite one line, but Linq helps:

var l = new List<List<List<double>>>(
    Enumerable.Range(0, array3D.GetLength(0)).Select(i0 => new List<List<double>>(
        Enumerable.Range(0, array3D.GetLength(1)).Select(i1 => new List<double>(
            Enumerable.Range(0, array3D.GetLength(2)).Select(i2 => array3D[i0, i1, i2])
        ))
    )));

I still would emphasize that this seems to be something which would be better suited to a custom class. The names Matrix, Sequence and Set come to mind...

answered Sep 1, 2014 at 3:11

Mitch

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