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

You should implement your own IEqualityComparer> and then use that in Distinct().

The choice of hash code in the IEqualityComparer depends on your actual data, but I think something like this should be adequate if your actual data resemble those in your examples:

class UnorderedQeuenceComparer : IEqualityComparer>
{
    public bool Equals(IEnumerable x, IEnumerable y)
    {
        return x.OrderBy(i => i).SequenceEqual(y.OrderBy(i => i));
    }

    public int GetHashCode(IEnumerable obj)
    {
        return obj.Sum(i => i * i);
    }
}

The important part is that GetHashCode() should be O(N), sorting would be too slow.