Create a dynamically dimensioned Array or List

Question

I want to create an Array or a List with N-Dimensions.

Is there a way to do this without having a Method for each possible dimension:

private ____ createArray(int dimensions, int[] lengths)
{
    // declare array with dimensions from variable dimensions
    // set length of first dimension to lengths[0]
    // set length of second dimension to lengths[1]
    // [...] 
    // return array
}

And not like this

private int[][][] create3DArray(int[] lengths)
{
    int[][][] array = new int[lengths[0]][][];

    int[] newLengths = new int[lengths.Count - 1];

    for(int i = 0; i < lengths.Count - 1; i++)
    {
        newLengths[i] = lengths[i + 1];
    }

    for(int i = 0; i < lengths[0]; i++)
    {
        array[i] = create2DArray(newLengths);
    }

    return array;
}

private int[][] create2DArray(int[] lengths)
{
    int[][] array = new int[lengths[0]][];

    for(int i = 0; i < lengths.Count; i++)
    {
        array[i] = new int[lengths[1]];
    }

    return array;
}

If I have to do it like this, I need to have a method for every possible (let's ignore the fact that it may not make sense to have an array with N-Dimensions) amount of dimensions.

List "dimension" is flexible enough I think, you may just need to initialize its value? — Ian
– Ian, Commented Feb 1, 2016 at 9:53
There is the Array.CreateInstance method, but it creates a multi-dimensional array and not a jagged array like you want. — Dirk
– Dirk, Commented Feb 1, 2016 at 9:59
@Ian How would I create a List, which I could use like a 4D-Array? Like list[i][j][k][l] = // fill with some random number — S. Jerk
– S. Jerk, Commented Feb 1, 2016 at 10:00
@Dirk Array.CreateInstance seems like it could do what i want. :) — S. Jerk
– S. Jerk, Commented Feb 1, 2016 at 10:11

rdn87 · Accepted Answer · 2016-02-01 09:58:47Z

2

you can create a list of lists:

var myList = new List<List<int>>();
for(int i = 0; i < 10; ++i) {
    var localList = new List<int>();
    myList.Add(localList);
}

answered Feb 1, 2016 at 9:58

rdn87

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1 Comment

S. Jerk Over a year ago

And if I want the List to contain a List which contains a List [...] (as many times as i want) and then return that list?

Ian · Accepted Answer · 2016-02-01 10:02:13Z

1

You could create like this using Enumerable.Repeat as many levels as you want:

int x = 5, y = 6, z = 7;
List<List<List<int>>> list3D = Enumerable.Repeat<List<List<int>>>(
    new List<List<int>>(
        Enumerable.Repeat<List<int>>(
            new List<int>(
                    Enumerable.Repeat<int>(0, z)
                    ), y)
        ), x
    ).ToList();
}

In the example above you create 3D lists with initial value of 0 and initial size of 5x6x7

answered Feb 1, 2016 at 10:02

Ian

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6 Comments

S. Jerk Over a year ago

This gets in the right direction. But if i want to make it with N-Dimensions? Instead of 3?

Ian Over a year ago

Then just add another level. Notice that the pattern is simply Enumerable.Repeat

S. Jerk Over a year ago

...but i have to add another level if i want more dimensions, which is exactly what i don't want.

Ian Over a year ago

I get what you mean, in that case you need to have a recursive call. Makes a generic method, then wrap the previous list in a list

Dirk Over a year ago

This method has a serious flaw in that the inner lists are all identical references. If you set list3D[0][1][2] = 4 then all list3D[x][y][2] == 4.

|

Daniel Kerr · Accepted Answer · 2020-03-09 22:35:40Z

0

It is possible.

Make an int array of dimensions. From there, you can create a conditional var declaration. The only trick is that you need to make explicit the conversion to (Array)

answered Mar 9, 2020 at 22:35

Daniel Kerr

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