TransposeSelfOrginizingList.cs

namespace AlgorithmsAndDataStructures.DataStructures.SelfOrganizingList;

public class TransposeSelfOrginizingList<T>
{
    private SelfOrganizingListNode<T> tail;

    public SelfOrganizingListNode<T> Head { get; private set; }

    public void Add(T value)
    {
        if (Head == null)
        {
            Head = new SelfOrganizingListNode<T> { Value = value };
            tail = Head;
            return;
        }

        tail.Next = new SelfOrganizingListNode<T> { Value = value };
        tail = tail.Next;
    }

    public SelfOrganizingListNode<T> Get(T value)
    {
        if (Head == null) return null;

        if (Head.Value.Equals(value)) return Head;

        if (Head.Next == null) return null;

        if (Head.Next.Value.Equals(value))
        {
            var tmp = Head.Next;
            Head.Next = tmp.Next;
            tmp.Next = Head;
            Head = tmp;

            return tmp;
        }

        var current = Head.Next.Next;
        var prePrevious = Head;
        var previous = Head.Next;

        while (current != null)
        {
            if (current.Value.Equals(value))
            {
                Swap(prePrevious, previous, current);
                return current;
            }

            prePrevious = previous;
            previous = previous.Next;
            current = previous.Next;
        }

        return null;
    }

    private static void Swap(SelfOrganizingListNode<T> prePrevious, SelfOrganizingListNode<T> previous,
        SelfOrganizingListNode<T> current)
    {
        prePrevious.Next = current;
        previous.Next = current.Next;
        current.Next = previous;
    }
}