public static void ShellSort(int[] data) {
  int inner, outer;
  int temp;
  int len = data.length;
  int h = 1;
  while (h <= len / 3)
      h = h * 3 + 1;

  while (h > 0) {
      for (outer = h; outer < len; outer++) {
          temp = data[outer];
          inner = outer;
          while (inner > h - 1 && data[inner - h] < temp) {
              data[inner] = data[inner - h];
              inner -= h;
          }
          data[inner] = temp;
      }
      h = (h - 1) / 3; // decrease h
  }
}