public void CycleShiftByBlocks(ref String strarr, int rotdist)
{
    int n = strarr.Length;
    if (rotdist == 0 || rotdist == n) return;
 
    int i, j, p;
    i = p = rotdist;
    j = n - p;
    while (i != j)
    {
        if (i > j) {
            this.StrSwap(ref strarr, p - i, p, j);
            i -= j;
        } else {
            this.StrSwap(ref strarr, p - i, p + j - i, i);
            j -= i;
        }
    }
    this.StrSwap(ref strarr, p - i, p, i);
}