N-Ary/Multiple-List Cartesian Product

Question

in Product SKUs, we can get Cartesian Product in the way of LINQ:

string[] arr1 = new[] {"red", "blue", "orange"};
string[] arr2 = new[] {"5 inche", "8 inch"};
var result = from a in arr1
             from b in arr2
             select a + " " + b;
foreach (var item in result){
    Console.WriteLine(item);
}

We know the exact number of arrays.

My question is: If the number of arrays is dynamic, how do we get Cartesian Product?

Thanks.

You need to be more precise - you have `arr1` & `arr2` and then you talk about `array`. Which are you referring to? Both? Or are you saying if you have multiple arrays and not just two? — Enigmativity, Nov 17 '14 at 04:29

score 3 · Answer 1 · answered Nov 17 '14 at 23:51

3

I liked Raeen's answer and it made me think of a simple linq way to solve this problem. This is a very similar method, but doesn't involve any state external to the computation.

var list = new List<IEnumerable<string>>()
{
    new[] {"red", "blue", "orange"},
    new[] {"5 inche", "8 inch"},
    new[] {"x", "y"},
};

var result =
    list
        .Aggregate((rs, vs) =>
            from r in rs
            from v in vs
            select r + " " + v)
        .ToList();

answered Nov 17 '14 at 23:51

Enigmativity

113,464
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+1. I think this is *a lot* prettier than the accepted answer due to no mutable state outside of `Aggregate`. May I suggest adding `list.DefaultIfEmpty(Enumerable.Empty())` before the call to `Aggregate` so as to avoid the `InvalidOperationException` if `list.Count` is zero? – Kirill Shlenskiy Nov 18 '14 at 00:55

score 0 · Accepted Answer · edited May 23 '17 at 12:05

0

I'd put them in a list of string arrays. Then I'd use ForEach:

IEnumerable<string> result = list.First();

list.RemoveAt(0);

list.ForEach(delegate(IEnumerable<string> value)
{
     result = (from r in result
               from v in value
               select r + " " + v).ToList();

});

You can also see this link : Cartesian Product for Group members

edited May 23 '17 at 12:05

Community

1
1

answered Nov 17 '14 at 06:14

Raein Hashemi

3,346
4
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33

@Enigmativity If we have many arrays and we don't know the count of them, the only way I can think of is a ForEach on the list and every time, we use that Linq on every array and the previous results we got from the previous arrays. See the link for another example. – Raein Hashemi Nov 17 '14 at 13:34
1

Very clever. I generally try to avoid state and use recursion instead for these kinds of things. Interesting approach. – Enigmativity Nov 17 '14 at 22:52

N-Ary/Multiple-List Cartesian Product

2 Answers2

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