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+/*
+ Copyright (c) Marshall Clow 2011-2012.
+
+ Distributed under 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)
+*/
+
+/// \file is_permutation.hpp
+/// \brief Is a sequence a permutation of another sequence
+/// \author Marshall Clow
+
+#ifndef BOOST_ALGORITHM_IS_PERMUTATION_HPP
+#define BOOST_ALGORITHM_IS_PERMUTATION_HPP
+
+#include <algorithm> // for std::less, tie, mismatch and is_permutation (if available)
+#include <utility> // for std::make_pair
+#include <functional> // for std::equal_to
+#include <iterator>
+
+#include <boost/range/begin.hpp>
+#include <boost/range/end.hpp>
+#include <boost/utility/enable_if.hpp>
+#include <boost/type_traits/is_same.hpp>
+#include <boost/tr1/tr1/tuple> // for tie
+
+namespace boost { namespace algorithm {
+
+#if __cplusplus >= 201103L
+// Use the C++11 versions of is_permutation if it is available
+using std::is_permutation; // Section 25.2.12
+#else
+/// \cond DOXYGEN_HIDE
+namespace detail {
+ template <typename Predicate, typename Iterator>
+ struct value_predicate {
+ value_predicate ( Predicate p, Iterator it ) : p_ ( p ), it_ ( it ) {}
+
+ template <typename T1>
+ bool operator () ( const T1 &t1 ) const { return p_ ( *it_, t1 ); }
+ private:
+ Predicate &p_;
+ Iterator it_;
+ };
+}
+/// \endcond
+
+
+/// \fn is_permutation ( ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 first2, BinaryPredicate p )
+/// \brief Tests to see if a the sequence [first,last) is a permutation of the sequence starting at first2
+///
+/// \param first The start of the input sequence
+/// \param last One past the end of the input sequence
+/// \param first2 The start of the second sequence
+/// \param p The predicate to compare elements with
+///
+/// \note This function is part of the C++2011 standard library.
+/// We will use the standard one if it is available,
+/// otherwise we have our own implementation.
+template< class ForwardIterator1, class ForwardIterator2, class BinaryPredicate >
+bool is_permutation ( ForwardIterator1 first1, ForwardIterator1 last1,
+ ForwardIterator2 first2, BinaryPredicate p )
+{
+// Skip the common prefix (if any)
+// std::tie (first1, first2) = std::mismatch (first1, last1, first2, p);
+ std::pair<ForwardIterator1, ForwardIterator2> eq = std::mismatch (first1, last1, first2, p);
+ first1 = eq.first;
+ first2 = eq.second;
+ if ( first1 != last1 ) {
+ // Create last2
+ ForwardIterator2 last2 = first2;
+ std::advance ( last2, std::distance (first1, last1));
+
+ // for each unique value in the sequence [first1,last1), count how many times
+ // it occurs, and make sure it occurs the same number of times in [first2, last2)
+ for ( ForwardIterator1 iter = first1; iter != last1; ++iter ) {
+ detail::value_predicate<BinaryPredicate, ForwardIterator1> pred ( p, iter );
+
+ /* For each value we haven't seen yet... */
+ if ( std::find_if ( first1, iter, pred ) == iter ) {
+ std::size_t dest_count = std::count_if ( first2, last2, pred );
+ if ( dest_count == 0 || dest_count != (std::size_t) std::count_if ( iter, last1, pred ))
+ return false;
+ }
+ }
+ }
+
+ return true;
+}
+
+/// \fn is_permutation ( ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 first2 )
+/// \brief Tests to see if a the sequence [first,last) is a permutation of the sequence starting at first2
+///
+/// \param first The start of the input sequence
+/// \param last One past the end of the input sequence
+/// \param first2 The start of the second sequence
+/// \note This function is part of the C++2011 standard library.
+/// We will use the standard one if it is available,
+/// otherwise we have our own implementation.
+template< class ForwardIterator1, class ForwardIterator2 >
+bool is_permutation ( ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 first2 )
+{
+// How should I deal with the idea that ForwardIterator1::value_type
+// and ForwardIterator2::value_type could be different? Define my own comparison predicate?
+ return boost::algorithm::is_permutation ( first, last, first2,
+ std::equal_to<typename std::iterator_traits<ForwardIterator1>::value_type> ());
+}
+
+#endif
+
+/// \fn is_permutation ( const Range &r, ForwardIterator first2 )
+/// \brief Tests to see if a the sequence [first,last) is a permutation of the sequence starting at first2
+///
+/// \param r The input range
+/// \param first2 The start of the second sequence
+template <typename Range, typename ForwardIterator>
+bool is_permutation ( const Range &r, ForwardIterator first2 )
+{
+ return boost::algorithm::is_permutation (boost::begin (r), boost::end (r), first2 );
+}
+
+/// \fn is_permutation ( const Range &r, ForwardIterator first2, BinaryPredicate pred )
+/// \brief Tests to see if a the sequence [first,last) is a permutation of the sequence starting at first2
+///
+/// \param r The input range
+/// \param first2 The start of the second sequence
+/// \param pred The predicate to compare elements with
+///
+// Disable this template when the first two parameters are the same type
+// That way the non-range version will be chosen.
+template <typename Range, typename ForwardIterator, typename BinaryPredicate>
+typename boost::disable_if_c<boost::is_same<Range, ForwardIterator>::value, bool>::type
+is_permutation ( const Range &r, ForwardIterator first2, BinaryPredicate pred )
+{
+ return boost::algorithm::is_permutation (boost::begin (r), boost::end (r), first2, pred );
+}
+
+}}
+
+#endif // BOOST_ALGORITHM_IS_PERMUTATION_HPP