// Copyright (c) 2007  INRIA Sophia-Antipolis (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v5.5.1/Spatial_sorting/include/CGAL/Hilbert_sort_base.h $
// $Id: Hilbert_sort_base.h 5c41b10 2020-01-02T10:26:44+01:00 Mael Rouxel-Labbé
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
// Author(s)     : Christophe Delage

#ifndef CGAL_HILBERT_SORT_BASE_H
#define CGAL_HILBERT_SORT_BASE_H

#include <CGAL/config.h>
#include <algorithm>
#include <CGAL/algorithm.h>
#include <CGAL/use.h>

namespace CGAL {

namespace internal {

template <class RandomAccessIterator, class Cmp>
RandomAccessIterator
hilbert_split (RandomAccessIterator begin, RandomAccessIterator end,
               Cmp cmp = Cmp ())
{
  if (begin >= end)
    return begin;

#if defined(CGAL_HILBERT_SORT_WITH_MEDIAN_POLICY_CROSS_PLATFORM_BEHAVIOR)
  RandomAccessIterator middle = begin + (end - begin) / 2;
  CGAL::nth_element (begin, middle, end, cmp);
  return middle;
#else
  RandomAccessIterator middle = begin + (end - begin) / 2;
  std::nth_element (begin, middle, end, cmp);
  return middle;
#endif
}

} // namespace internal

} // namespace CGAL

#endif//CGAL_HILBERT_SORT_BASE_H
