LINQ implementation of Cartesian Product with pruning

Question

I hope someone is able to help me with what is, at least to me, quite a tricky algorithm.

The Problem

I have a List (1 <= size <= 5, but siz

Answer 1

void Main()
{
    var query =     from a in new int[] { 1 }
                    from b in new int[] { 2, 3 }
                    from c in new int[] { 2, 3 }
                    from d in new int[] { 4 }                   
                    from e in new int[] { 2, 3 }
                    select new int[] { a, b, c, d, e }; 
    query.Distinct(new ArrayComparer());
        //.Dump();
}
 public class ArrayComparer : IEqualityComparer
    {
        public bool Equals(int[] x, int[] y)
        {            
            if (x == null || y == null)
                return false;

            return x.OrderBy(i => i).SequenceEqual(y.OrderBy(i => i));

        }

        public int GetHashCode(int[] obj)
        {
            if ( obj == null || obj.Length == 0)
                return 0;
            var hashcode = obj[0];
            for (int i = 1; i < obj.Length; i++)
            {
                hashcode ^= obj[i];
            }
            return hashcode;
        }
    }