Arrays of int to one array

Question

Say I have following arrays of int:

var array1 = new[] {0, 2, 4, 6};
var array2 = new[] {0, 4, 5, 7};
var array3 = new[] {1, 4, 3, 5};

How do I merge this into one array of arrays so that the resulting is the list of all possible combinations of values in arrays? I.e. something similar to:

var resultingArray = new[] {new[] {0, 0, 1}, new[] {0, 4, 1}, new[] {0, 5, 1}....};

E.g. the length of arrays is the number of arrays I have but with the assumption that I do not know how many arrays I have and their length.

Possible duplicate of [Permutation of array](https://stackoverflow.com/questions/2920315/permutation-of-array) — xsami, Apr 11 '18 at 12:56
This is not permutation. Check the definition for permutation. — Azimuth, Apr 11 '18 at 13:08
I don't understand how [this topic](https://stackoverflow.com/questions/2920315/permutation-of-array) would help in my situation. — Azimuth, Apr 11 '18 at 13:16

LenglBoy · Answer 1 · 2018-04-11T13:00:37.083

2

You can´t merge them automatical and dynamic because your programm doesn´t know how manny and which arrays you got. But you can easyly create an Array of Arrays, because you can hardcode it, like this:

int resultingArray[][] = new int[3][]; // 3 = X maybe
resultingArray [0] = array1;
resultingArray [1] = array2;
resultingArray [2] = array3;
// ... up to X

It will look like this if you visualize the structure:

[[0,2,4,6], [...], [...]]

edited Apr 11 '18 at 13:00

answered Apr 11 '18 at 12:59

LenglBoy

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Ok, then I guess that is not possible. – Azimuth Apr 11 '18 at 13:00
The data structre will be exactly like you want it if you visualize it. – LenglBoy Apr 11 '18 at 13:01

Matthew Watson · Accepted Answer · 2018-04-11T13:04:13.010

This is known as the N-ary Cartesian Product.

Eric Lippert blogged a solution to this:

public static IEnumerable<IEnumerable<T>> Combine<T>(params IEnumerable<T>[] sequences)
{
    return Combine(sequences.AsEnumerable());
}

public static IEnumerable<IEnumerable<T>> Combine<T>(IEnumerable<IEnumerable<T>> sequences)
{
    IEnumerable<IEnumerable<T>> emptyProduct = new[] { Enumerable.Empty<T>() };

    return sequences.Aggregate(
        emptyProduct,
        (accumulator, sequence) =>
            from accseq in accumulator
            from item in sequence
            select accseq.Concat(new[] { item }));
}

This is how you could use it:

var array1 = new[] { 0, 2, 4, 6 };
var array2 = new[] { 0, 4, 5, 7 };
var array3 = new[] { 1, 4, 3, 5 };

var result = var result = Combine(array1, array2, array3);

var combinations = result.Select(x => x.ToArray()).ToArray();

foreach (var combination in combinations)
    Console.WriteLine(string.Join(", ", combination));

Note that you don't actually need to convert the resulting enumerables into arrays like I did above, unless you need to pass them to methods that expect arrays.

You can use result directly like so:

foreach (var combination in result)
    Console.WriteLine(string.Join(", ", combination));

But you need to enter all base-arrays by their name and you can´t do this manually. So this is very overloaded and complicated to read. But one way to do it. — LenglBoy, Apr 11 '18 at 13:04
Is there a generic solution? Say I don't know how many array I have and how long they are. — Azimuth, Apr 11 '18 at 13:08
@Azimuth This *is* a generic solution. You can pass any number of arrays of any length (each array could be a different length). — Matthew Watson, Apr 11 '18 at 13:08

Arrays of int to one array

2 Answers2