PointerHeadTailAdder.cs

internal unsafe class PointerHeadTailAdder : IIntegerAdder
{

    public int Add(int[] values)
    {
        fixed (int* head = values)
        {
            return AddImplementation(head, values.Length);
        }
    }

    private static int AddImplementation(int *head, int length)
    {
        if (length == 0)
        {
            return 0;
        }
        return *head + AddImplementation(++head, --length);
    }

}