template <typename T>
  bool
  next_permutation(T first, T last)
  {
    if (first == last) return false;

    auto x_item = last;

    for (T i = first; i != (last - 1); ++i)
      if (*i < *(i + 1)) x_item = i;

    if (x_item == last) return false;

    auto y_item = last;

    for (T i = first; i != last; ++i)
      if (*x_item < *i) y_item = i;

    if (y_item == last) return false;

    std::iter_swap(x_item, y_item);

    ++x_item;

    while ((x_item != last) && (x_item != --last))
      std::iter_swap(x_item++, last);

    return true;
  }