37762726-CartesianProduct, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5
//http://stackoverflow.com/questions/37762726/how-to-combine-elements-of-a-matrix-without-using-the-same-row-more-than-once-ea/37763185?noredirect=1#comment62995278_37763185

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public static class Extensions
    {
        public static IEnumerable<IEnumerable<T>> CartesianProduct<T>(this 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}));
        }
    }

public class Program
    {
        public static void Main(string[] args)
        {
            var s1 = new[] {'a', 'b'};
            var s2 = new[] {'x', 'c'};
            var product =
                from first in s1
                from second in s2
                select new { a=first, b=second };
            
            foreach (var item in product)
                Console.Write("{0}{1}\t",item.a, item.b);
            
            ////////////////////////////////////////
            Console.WriteLine();
            var s = new [] {s1, s2};
            var cp = s.CartesianProduct ();
            foreach (var e1 in cp)
            {
                foreach (var e2 in e1)    
                {
                    Console.Write(e2);
                    Console.Write("\t");
                }
                Console.WriteLine();
            }
            
            ////////////////////////////////////////
            s1 = new[] {'A', 'B', 'F'};
            s2 = new[] {'X', 'C', 'D'};
            var s3 = new[] {'P','O','K'};

Console.WriteLine();
            s = new [] {s1, s2, s3};
            cp = s.CartesianProduct ();
            foreach (var e1 in cp)
            {
                foreach (var e2 in e1)    
                {
                    Console.Write(e2);
                    Console.Write("\t");
                }
                Console.WriteLine();
            }
        }

}
}

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Compilation time: 0,23 sec, absolute running time: 0,16 sec, cpu time: 0,14 sec, average memory usage: 14 Mb, average nr of threads: 3