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Linq - group list by pairs based on property

I have a list of objects with a property that can be used to split objects into pairs. I know in advance that each object is part of a pair.

Here is an example illustrating the situation:

<h / "> I have a list of individual shoes that I would like to pair in pairs.

Let's say my list is as follows:

List<Shoe> shoes = new List<Shoe>();

shoes.Add(new Shoe { Id = 19, Brand = "Nike", LeftOrRight = LeftOrRight.L });
shoes.Add(new Shoe { Id = 29, Brand = "Nike", LeftOrRight = LeftOrRight.R });
shoes.Add(new Shoe { Id = 11, Brand = "Nike", LeftOrRight = LeftOrRight.L });
shoes.Add(new Shoe { Id = 60, Brand = "Nike", LeftOrRight = LeftOrRight.R });
shoes.Add(new Shoe { Id = 65, Brand = "Asics", LeftOrRight = LeftOrRight.L });
shoes.Add(new Shoe { Id = 82, Brand = "Asics", LeftOrRight = LeftOrRight.R });

I would like to display these shoes as pairs, for example:

Pair:
Id: 19, Brand: Nike, LeftOrRight: L
Id: 29, Brand: Nike, LeftOrRight: R

Pair:
Id: 11, Brand: Nike, LeftOrRight: L
Id: 60, Brand: Nike, LeftOrRight: R

Pair:
Id: 65, Brand: Asics, LeftOrRight: L
Id: 82, Brand: Asics, LeftOrRight: R

Please note that individual shoes can only exist as part of one pair.

, :

var pairsByBrand = shoes.GroupBy(s => s.Brand);
foreach (var group in pairsByBrand)
{
    Console.WriteLine("Pair:");
    foreach (var shoe in group)
    {
        Console.WriteLine(shoe);
    }
    Console.WriteLine();
}

?

+5
3
var shoesByBrand = shoes.GroupBy(s => s.Brand);
foreach (var byBrand in shoesByBrand)
{
    var lefts = byBrand.Where(s => s.LeftOrRight == LeftOrRight.L);
    var rights = byBrand.Where(s => s.LeftOrRight == LeftOrRight.R);
    var pairs = lefts.Zip(rights,(l, r) => new {Left = l, Right = r});

    foreach(var p in pairs)
    {
        Console.WriteLine("Pair:  {{{0}, {1}}}", p.Left.Id, p.Right.Id);
    }

    Console.WriteLine();
}

. , . , .

+3

LINQ, SelectMany Zip, IEnumerable of Tuple s:

IEnumerable<Tuple<Shoe, Shoe>> pairs = shoes
    .GroupBy(shoe => shoe.Brand)
    .SelectMany(brand=>
        Enumerable.Zip(
            brand.Where(shoe=>shoe.LeftOrRight == LeftOrRight.L),
            brand.Where(shoe=>shoe.LeftOrRight == LeftOrRight.R),
            Tuple.Create
        )
    );
+7

:

var pairs = shoes.GroupBy(s => s.Brand)
                 .Select(g => g.GroupBy(s => s.LeftOrRight));
                 .SelectMany(Enumerable.Zip(g => g.First(), g => g.Last(),Tuple.Create));

, ( Thom Smith) , , . , , .

What he does is group shoes by brand, and then left / right in each brand. Then he goes into a random match of the left shoes of each brand with the right shoes of the same, doing this for all brands in turn.

+2
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