//  (C) Copyright Herve Bronnimann 2004.

//  Use, modification and distribution are subject to the

//  Boost Software License, Version 1.0. (See accompanying file

//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

/*

 Revision history:

   1 July 2004

      Split the code into two headers to lessen dependence on

      Boost.tuple. (Herve)

   26 June 2004

      Added the code for the boost minmax library. (Herve)

*/

#ifndef BOOST_ALGORITHM_MINMAX_ELEMENT_HPP

#define BOOST_ALGORITHM_MINMAX_ELEMENT_HPP

/* PROPOSED STANDARD EXTENSIONS:

 *

 * minmax_element(first, last)

 * Effect: std::make_pair( std::min_element(first, last),

 *                         std::max_element(first, last) );

 *

 * minmax_element(first, last, comp)

 * Effect: std::make_pair( std::min_element(first, last, comp),

 *                         std::max_element(first, last, comp) );

 */

#include <utility> // for std::pair and std::make_pair

namespace boost {

  namespace detail {  // for obtaining a uniform version of minmax_element

    // that compiles with VC++ 6.0 -- avoid the iterator_traits by

    // having comparison object over iterator, not over dereferenced value

    template <typename Iterator>

    struct less_over_iter {

      bool operator()(Iterator const& it1,

                      Iterator const& it2) const { return *it1 < *it2; }

    };

    template <typename Iterator, class BinaryPredicate>

    struct binary_pred_over_iter {

      explicit binary_pred_over_iter(BinaryPredicate const& p ) : m_p( p ) {}

      bool operator()(Iterator const& it1,

                      Iterator const& it2) const { return m_p(*it1, *it2); }

    private:

      BinaryPredicate m_p;

    };

    // common base for the two minmax_element overloads

    template <typename ForwardIter, class Compare >

    std::pair<ForwardIter,ForwardIter>

    basic_minmax_element(ForwardIter first, ForwardIter last, Compare comp)

    {

      if (first == last)

        return std::make_pair(last,last);

      ForwardIter min_result = first;

      ForwardIter max_result = first;

      // if only one element

      ForwardIter second = first; ++second;

      if (second == last)

        return std::make_pair(min_result, max_result);

      // treat first pair separately (only one comparison for first two elements)

      ForwardIter potential_min_result = last;

      if (comp(first, second))

        max_result = second;

      else {

        min_result = second;

        potential_min_result = first;

      }

      // then each element by pairs, with at most 3 comparisons per pair

      first = ++second; if (first != last) ++second;

      while (second != last) {

        if (comp(first, second)) {

          if (comp(first, min_result)) {

            min_result = first;

            potential_min_result = last;

          }

          if (comp(max_result, second))

            max_result = second;

        } else {

          if (comp(second, min_result)) {

            min_result = second;

            potential_min_result = first;

          }

          if (comp(max_result, first))

            max_result = first;

        }

        first = ++second;

        if (first != last) ++second;

      }

      // if odd number of elements, treat last element

      if (first != last) { // odd number of elements

        if (comp(first, min_result))

          min_result = first, potential_min_result = last;

        else if (comp(max_result, first))

          max_result = first;

      }

      // resolve min_result being incorrect with one extra comparison

      // (in which case potential_min_result is necessarily the correct result)

      if (potential_min_result != last

        && !comp(min_result, potential_min_result))

        min_result = potential_min_result;

      return std::make_pair(min_result,max_result);

    }

  } // namespace detail

  template <typename ForwardIter>

  std::pair<ForwardIter,ForwardIter>

  minmax_element(ForwardIter first, ForwardIter last)

  {

    return detail::basic_minmax_element(first, last,

             detail::less_over_iter<ForwardIter>() );

  }

  template <typename ForwardIter, class BinaryPredicate>

  std::pair<ForwardIter,ForwardIter>

  minmax_element(ForwardIter first, ForwardIter last, BinaryPredicate comp)

  {

    return detail::basic_minmax_element(first, last,

             detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );

  }

}

/* PROPOSED BOOST EXTENSIONS

 * In the description below, [rfirst,rlast) denotes the reversed range

 * of [first,last). Even though the iterator type of first and last may

 * be only a Forward Iterator, it is possible to explain the semantics

 * by assuming that it is a Bidirectional Iterator. In the sequel,

 * reverse(ForwardIterator&) returns the reverse_iterator adaptor.

 * This is not how the functions would be implemented!

 *

 * first_min_element(first, last)

 * Effect: std::min_element(first, last);

 *

 * first_min_element(first, last, comp)

 * Effect: std::min_element(first, last, comp);

 *

 * last_min_element(first, last)

 * Effect: reverse( std::min_element(reverse(last), reverse(first)) );

 *

 * last_min_element(first, last, comp)

 * Effect: reverse( std::min_element(reverse(last), reverse(first), comp) );

 *

 * first_max_element(first, last)

 * Effect: std::max_element(first, last);

 *

 * first_max_element(first, last, comp)

 * Effect: max_element(first, last);

 *

 * last_max_element(first, last)

 * Effect: reverse( std::max_element(reverse(last), reverse(first)) );

 *

 * last_max_element(first, last, comp)

 * Effect: reverse( std::max_element(reverse(last), reverse(first), comp) );

 *

 * first_min_first_max_element(first, last)

 * Effect: std::make_pair( first_min_element(first, last),

 *                         first_max_element(first, last) );

 *

 * first_min_first_max_element(first, last, comp)

 * Effect: std::make_pair( first_min_element(first, last, comp),

 *                         first_max_element(first, last, comp) );

 *

 * first_min_last_max_element(first, last)

 * Effect: std::make_pair( first_min_element(first, last),

 *                         last_max_element(first, last) );

 *

 * first_min_last_max_element(first, last, comp)

 * Effect: std::make_pair( first_min_element(first, last, comp),

 *                         last_max_element(first, last, comp) );

 *

 * last_min_first_max_element(first, last)

 * Effect: std::make_pair( last_min_element(first, last),

 *                         first_max_element(first, last) );

 *

 * last_min_first_max_element(first, last, comp)

 * Effect: std::make_pair( last_min_element(first, last, comp),

 *                         first_max_element(first, last, comp) );

 *

 * last_min_last_max_element(first, last)

 * Effect: std::make_pair( last_min_element(first, last),

 *                         last_max_element(first, last) );

 *

 * last_min_last_max_element(first, last, comp)

 * Effect: std::make_pair( last_min_element(first, last, comp),

 *                         last_max_element(first, last, comp) );

 */

namespace boost {

  // Min_element and max_element variants

  namespace detail {  // common base for the overloads

  template <typename ForwardIter, class BinaryPredicate>

  ForwardIter

  basic_first_min_element(ForwardIter first, ForwardIter last,

                          BinaryPredicate comp)

  {

    if (first == last) return last;

    ForwardIter min_result = first;

    while (++first != last)

      if (comp(first, min_result))

        min_result = first;

    return min_result;

  }

  template <typename ForwardIter, class BinaryPredicate>

  ForwardIter

  basic_last_min_element(ForwardIter first, ForwardIter last,

                         BinaryPredicate comp)

  {

    if (first == last) return last;

    ForwardIter min_result = first;

    while (++first != last)

      if (!comp(min_result, first))

        min_result = first;

    return min_result;

  }

  template <typename ForwardIter, class BinaryPredicate>

  ForwardIter

  basic_first_max_element(ForwardIter first, ForwardIter last,

                          BinaryPredicate comp)

  {

    if (first == last) return last;

    ForwardIter max_result = first;

    while (++first != last)

      if (comp(max_result, first))

        max_result = first;

    return max_result;

  }

  template <typename ForwardIter, class BinaryPredicate>

  ForwardIter

  basic_last_max_element(ForwardIter first, ForwardIter last,

                         BinaryPredicate comp)

  {

    if (first == last) return last;

    ForwardIter max_result = first;

    while (++first != last)

      if (!comp(first, max_result))

        max_result = first;

    return max_result;

  }

  } // namespace detail

  template <typename ForwardIter>

  ForwardIter

  first_min_element(ForwardIter first, ForwardIter last)

  {

    return detail::basic_first_min_element(first, last,

             detail::less_over_iter<ForwardIter>() );

  }

  template <typename ForwardIter, class BinaryPredicate>

  ForwardIter

  first_min_element(ForwardIter first, ForwardIter last, BinaryPredicate comp)

  {

    return detail::basic_first_min_element(first, last,

             detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );

  }

  template <typename ForwardIter>

  ForwardIter

  last_min_element(ForwardIter first, ForwardIter last)

  {

    return detail::basic_last_min_element(first, last,

             detail::less_over_iter<ForwardIter>() );

  }

  template <typename ForwardIter, class BinaryPredicate>

  ForwardIter

  last_min_element(ForwardIter first, ForwardIter last, BinaryPredicate comp)

  {

    return detail::basic_last_min_element(first, last,

             detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );

  }

  template <typename ForwardIter>

  ForwardIter

  first_max_element(ForwardIter first, ForwardIter last)

  {

    return detail::basic_first_max_element(first, last,

             detail::less_over_iter<ForwardIter>() );

  }

  template <typename ForwardIter, class BinaryPredicate>

  ForwardIter

  first_max_element(ForwardIter first, ForwardIter last, BinaryPredicate comp)

  {

    return detail::basic_first_max_element(first, last,

             detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );

  }

  template <typename ForwardIter>

  ForwardIter

  last_max_element(ForwardIter first, ForwardIter last)

  {

    return detail::basic_last_max_element(first, last,

             detail::less_over_iter<ForwardIter>() );

  }

  template <typename ForwardIter, class BinaryPredicate>

  ForwardIter

  last_max_element(ForwardIter first, ForwardIter last, BinaryPredicate comp)

  {

    return detail::basic_last_max_element(first, last,

             detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );

  }

  // Minmax_element variants -- comments removed

  namespace detail {

  template <typename ForwardIter, class BinaryPredicate>

  std::pair<ForwardIter,ForwardIter>

  basic_first_min_last_max_element(ForwardIter first, ForwardIter last,

                                   BinaryPredicate comp)

  {

    if (first == last)

      return std::make_pair(last,last);

    ForwardIter min_result = first;

    ForwardIter max_result = first;

    ForwardIter second = ++first;

    if (second == last)

      return std::make_pair(min_result, max_result);

    if (comp(second, min_result))

      min_result = second;

    else

      max_result = second;

    first = ++second; if (first != last) ++second;

    while (second != last) {

      if (!comp(second, first)) {

        if (comp(first, min_result))

                 min_result = first;

        if (!comp(second, max_result))

          max_result = second;

      } else {

        if (comp(second, min_result))

          min_result = second;

        if (!comp(first, max_result))

              max_result = first;

      }

      first = ++second; if (first != last) ++second;

    }

    if (first != last) {

      if (comp(first, min_result))

         min_result = first;

      else if (!comp(first, max_result))

               max_result = first;

    }

    return std::make_pair(min_result, max_result);

  }

  template <typename ForwardIter, class BinaryPredicate>

  std::pair<ForwardIter,ForwardIter>

  basic_last_min_first_max_element(ForwardIter first, ForwardIter last,

                                   BinaryPredicate comp)

  {

    if (first == last) return std::make_pair(last,last);

    ForwardIter min_result = first;

    ForwardIter max_result = first;

    ForwardIter second = ++first;

    if (second == last)

      return std::make_pair(min_result, max_result);

    if (comp(max_result, second))

      max_result = second;

    else

      min_result = second;

    first = ++second; if (first != last) ++second;

    while (second != last)  {

      if (comp(first, second)) {

        if (!comp(min_result, first))

          min_result = first;

        if (comp(max_result, second))

          max_result = second;

      } else {

        if (!comp(min_result, second))

          min_result = second;

        if (comp(max_result, first))

          max_result = first;

      }

      first = ++second; if (first != last) ++second;

    }

    if (first != last) {

      if (!comp(min_result, first))

        min_result = first;

      else if (comp(max_result, first))

        max_result = first;

    }

    return std::make_pair(min_result, max_result);

  }

  template <typename ForwardIter, class BinaryPredicate>

  std::pair<ForwardIter,ForwardIter>

  basic_last_min_last_max_element(ForwardIter first, ForwardIter last,

                                  BinaryPredicate comp)

  {

    if (first == last) return std::make_pair(last,last);

    ForwardIter min_result = first;

    ForwardIter max_result = first;

    ForwardIter second = first; ++second;

    if (second == last)

      return std::make_pair(min_result,max_result);

    ForwardIter potential_max_result = last;

    if (comp(first, second))

      max_result = second;

    else {

      min_result = second;

      potential_max_result = second;

    }

    first = ++second; if (first != last) ++second;

    while (second != last) {

      if (comp(first, second)) {

        if (!comp(min_result, first))

          min_result = first;

        if (!comp(second, max_result)) {

          max_result = second;

          potential_max_result = last;

        }

      } else {

        if (!comp(min_result, second))

          min_result = second;

        if (!comp(first, max_result)) {

          max_result = first;

          potential_max_result = second;

        }

      }

      first = ++second;

      if (first != last) ++second;

    }

    if (first != last) {

      if (!comp(min_result, first))

        min_result = first;

      if (!comp(first, max_result)) {

        max_result = first;

               potential_max_result = last;

      }

    }

    if (potential_max_result != last

        && !comp(potential_max_result, max_result))

      max_result = potential_max_result;

    return std::make_pair(min_result,max_result);

  }

  } // namespace detail

  template <typename ForwardIter>

  inline std::pair<ForwardIter,ForwardIter>

  first_min_first_max_element(ForwardIter first, ForwardIter last)

  {

    return minmax_element(first, last);

  }

  template <typename ForwardIter, class BinaryPredicate>

  inline std::pair<ForwardIter,ForwardIter>

  first_min_first_max_element(ForwardIter first, ForwardIter last,

                              BinaryPredicate comp)

  {

    return minmax_element(first, last, comp);

  }

  template <typename ForwardIter>

  std::pair<ForwardIter,ForwardIter>

  first_min_last_max_element(ForwardIter first, ForwardIter last)

  {

    return detail::basic_first_min_last_max_element(first, last,

             detail::less_over_iter<ForwardIter>() );

  }

  template <typename ForwardIter, class BinaryPredicate>

  inline std::pair<ForwardIter,ForwardIter>

  first_min_last_max_element(ForwardIter first, ForwardIter last,

                              BinaryPredicate comp)

  {

    return detail::basic_first_min_last_max_element(first, last,

             detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );

  }

  template <typename ForwardIter>

  std::pair<ForwardIter,ForwardIter>

  last_min_first_max_element(ForwardIter first, ForwardIter last)

  {

    return detail::basic_last_min_first_max_element(first, last,

             detail::less_over_iter<ForwardIter>() );

  }

  template <typename ForwardIter, class BinaryPredicate>

  inline std::pair<ForwardIter,ForwardIter>

  last_min_first_max_element(ForwardIter first, ForwardIter last,

                              BinaryPredicate comp)

  {

    return detail::basic_last_min_first_max_element(first, last,