Flattening object of arrays

Question

I have an object "Compact" that consists of an ID and two arrays:

public class Compact
    {
        public int Id { get; set; }
        public int[] Number { get; set; }
        public double[] Value { get; set; }

        public Compact(int id, int[] number,  double[] value)
        {
            Id = id;
            Number = number;
            Value = value;
        }
    }

A list of Compact objects can be initialized like this:

List<Compact> c = new List<Compact>
        {
            new Compact(1, new int[] { 1, 2, 3 }, new double[] { 0.05, 0.02, 0.03 }),
            new Compact(2, new int[] { 1, 2, 3 }, new double[] { 0.07, 0.01, 0.04 }),
            new Compact(3, new int[] { 1, 2, 3 }, new double[] { 0.02, 0.025, 0.05 })
        };

I am looking for an elegant way to flatten this object into the object "Flattened":

public class Flattened
    {
        public int Id { get; set; }
        public int Number { get; set; }
        public double Value { get; set; }

        public Flattened(int id, int number, double value)
        {
            Id = id;
            Number = number;
            Value = value;
        }
    }

The result of the flattening would correspond to this:

List<Flattened> f = new List<Flattened>
        {
            new Flattened(1,1,0.05),
            new Flattened(1,2,0.02),
            new Flattened(1,3,0.03),
            new Flattened(2,1,0.07),
            new Flattened(2,2,0.01),
            new Flattened(2,3,0.04),
            new Flattened(3,1,0.02),
            new Flattened(3,2,0.025),
            new Flattened(3,3,0.05)
        };

I am able to do the flattening using loops, but I am wondering whether there are more suited methods in terms of performance, like a Linq operation or a different collection-type?

Answer 1

You can run simply for loops.

List<Compact> ls = new List<Compact>
{
    new Compact(1, new int[] { 1, 2, 3 }, new double[] { 0.05, 0.02, 0.03 }),
    new Compact(2, new int[] { 1, 2, 3 }, new double[] { 0.07, 0.01, 0.04 }),
    new Compact(3, new int[] { 1, 2, 3 }, new double[] { 0.02, 0.025, 0.05 })
};
List<Flattened> ls2 = new List<Flattened>();
foreach (Compact compact in ls)
{
    for (var index = 0; index < compact.Number.Length; index++)
    {
        ls2.Add(new Flattened(compact.Id, compact.Number[index], compact.Value[index]));
    }
}

Note I have assumed that both arrays will have same number of items.

Answer 2

Using LINQ, you can do

c.SelectMany(
    x => x.Number.Zip(x.Value, (n, v) => new Flattened(x.Id, n, v))
).ToList()

SelectMany does the flattening, Zip , as its name suggests, "zips" the Number and Value arrays together, and apply the function (n, v) => new Flattened(x.Id, n, v) to each pair, creating a Flattened object from each pair.

Answer 3

You can use Linq for this, a combination of SelectMany and Zip should do the trick

(n, v) => (n, v) creates a tuple of pairs of Number and Value

List<Compact> ls = new List<Compact>
{
    new Compact(1, new int[] { 1, 2, 3 }, new double[] { 0.05, 0.02, 0.03 }),
    new Compact(2, new int[] { 1, 2, 3 }, new double[] { 0.07, 0.01, 0.04 }),
    new Compact(3, new int[] { 1, 2, 3 }, new double[] { 0.02, 0.025, 0.05 })
};

var flattened = ls
    .SelectMany(
        c => c.Number.Zip(c.Value, (n, v) => (n, v)),
        (c, nv) => new Flattened(c.Id, nv.n, nv.v)
    ).ToList();

dotnetfiddle