libcxx/include/__algorithm/minmax_element.h

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___ALGORITHM_MINMAX_ELEMENT_H
#define _LIBCPP___ALGORITHM_MINMAX_ELEMENT_H

#include <__config>
#include <__algorithm/comp.h>
#include <__iterator/iterator_traits.h>
#include <utility>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _ForwardIterator, class _Compare>
_LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX11
pair<_ForwardIterator, _ForwardIterator>
minmax_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
{
  static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
        "std::minmax_element requires a ForwardIterator");
  pair<_ForwardIterator, _ForwardIterator> __result(__first, __first);
  if (__first != __last)
  {
      if (++__first != __last)
      {
          if (__comp(*__first, *__result.first))
              __result.first = __first;
          else
              __result.second = __first;
          while (++__first != __last)
          {
              _ForwardIterator __i = __first;
              if (++__first == __last)
              {
                  if (__comp(*__i, *__result.first))
                      __result.first = __i;
                  else if (!__comp(*__i, *__result.second))
                      __result.second = __i;
                  break;
              }
              else
              {
                  if (__comp(*__first, *__i))
                  {
                      if (__comp(*__first, *__result.first))
                          __result.first = __first;
                      if (!__comp(*__i, *__result.second))
                          __result.second = __i;
                  }
                  else
                  {
                      if (__comp(*__i, *__result.first))
                          __result.first = __i;
                      if (!__comp(*__first, *__result.second))
                          __result.second = __first;
                  }
              }
          }
      }
  }
  return __result;
}

template <class _ForwardIterator>
_LIBCPP_NODISCARD_EXT inline
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
pair<_ForwardIterator, _ForwardIterator>
minmax_element(_ForwardIterator __first, _ForwardIterator __last)
{
    return _VSTD::minmax_element(__first, __last,
              __less<typename iterator_traits<_ForwardIterator>::value_type>());
}

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___ALGORITHM_MINMAX_ELEMENT_H