Does code exist, for shifting List elements to left or right by specified amount, in C#?

Question

Does code exist, for shifting List elements to left or right by specified amount, in C#?

It is tricky code, it will take some time to write and test special cases, I would rather reuse something if it exists.

Thanks

Answer 1

Something like this for shift left...

public static void ShiftLeft<T>(List<T> lst, int shifts)
{
    for (int i = shifts; i < lst.Count; i++)
    {
        lst[i - shifts] = lst[i];
    }

    for (int i = lst.Count - shifts; i < lst.Count; i++)
    {
        lst[i] = default(T);
    }
}

For shift right it's a little more tricky, because we must copy in reverse

public static void ShiftRight<T>(List<T> lst, int shifts)
{
    for (int i = lst.Count - shifts - 1; i >= 0; i--)
    {
        lst[i + shifts] = lst[i];
    }

    for (int i = 0; i < shifts; i++)
    {
        lst[i] = default(T);
    }
}

With arrays it's a lot more simple, because Array has very powerful methods:

public static void ShiftLeft<T>(T[] arr, int shifts)
{
    Array.Copy(arr, shifts, arr, 0, arr.Length - shifts);
    Array.Clear(arr, arr.Length - shifts, shifts);
}

public static void ShiftRight<T>(T[] arr, int shifts)
{
    Array.Copy(arr, 0, arr, shifts, arr.Length - shifts);
    Array.Clear(arr, 0, shifts);
}

And yes, Array.Copy is protected against overleap: If sourceArray and destinationArray overlap, this method behaves as if the original values of sourceArray were preserved in a temporary location before destinationArray is overwritten.