Fastest algorithm for circle shift N sized array for M position

Question

What is the fastest algorithm for circle shifting array for M positions?
For example, [3 4 5 2 3 1 4] shift M = 2 positions should be [1 4 3 4 5 2 3

Answer 1

Similar to @IsaacTurner and not that elegant due to unnecessary copying, but implementation is quite short.

The idea - swap element A on index 0 with the element B which sits on destination of A. Now B is first. Swap it with the element C which sits on destination of B. Continue until the destination is not at 0.

If the greatest common divisor is not 1 then you're not finished yet - you need to continue swapping, but now using index 1 at your starting and end point.

Continue until your starting position is not the gcd.

int gcd(int a, int b) => b == 0 ? a : gcd(b, a % b);

public int[] solution(int[] A, int K)
{
    for (var i = 0; i < gcd(A.Length, K); i++)
    {
        for (var j = i; j < A.Length - 1; j++)
        {
            var destIndex = ((j-i) * K + K + i) % A.Length;
            if (destIndex == i) break;
            var destValue = A[destIndex];
            A[destIndex] = A[i];
            A[i] = destValue;
        }
    }

    return A;
}