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Better 'is_permutation' implementation, tests

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[SVN r84389]
This commit is contained in:
Marshall Clow
2013-05-20 15:37:50 +00:00
parent a4b907197e
commit b9d89c559b
5 changed files with 414 additions and 341 deletions
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159
include/boost/algorithm/cxx11/is_permutation.hpp
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@ -24,10 +24,6 @@
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>
@ -37,18 +33,82 @@ namespace detail {
template <typename T1>
bool operator () ( const T1 &t1 ) const { return p_ ( *it_, t1 ); }
private:
Predicate &p_;
Predicate p_;
Iterator it_;
};
// Preconditions:
// 1. The sequences are the same length
// 2. Any common elements on the front have been removed (not necessary for correctness, just for performance)
template< class ForwardIterator1, class ForwardIterator2, class BinaryPredicate >
bool is_permutation_inner ( ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate p ) {
// 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 ) {
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;
}
template< class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
bool is_permutation_tag ( ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate p,
std::forward_iterator_tag, std::forward_iterator_tag ) {
// Skip the common prefix (if any)
while ( first1 != last1 && first2 != last2 && p ( *first1, *first2 )) {
++first1;
++first2;
}
if ( first1 != last1 && first2 != last2 )
return boost::algorithm::detail::is_permutation_inner ( first1, last1, first2, last2,
std::equal_to<typename std::iterator_traits<ForwardIterator1>::value_type> ());
return first1 == last1 && first2 == last2;
}
template <class RandomAccessIterator1, class RandomAccessIterator2, class BinaryPredicate>
bool is_permutation_tag ( RandomAccessIterator1 first1, RandomAccessIterator1 last1,
RandomAccessIterator2 first2, RandomAccessIterator2 last2,
BinaryPredicate p,
std::random_access_iterator_tag, std::random_access_iterator_tag ) {
// Cheap check
if ( std::distance ( first1, last1 ) != std::distance ( first2, last2 ))
return false;
// Skip the common prefix (if any)
while ( first1 != last1 && first2 != last2 && p ( *first1, *first2 )) {
++first1;
++first2;
}
if ( first1 != last1 && first2 != last2 )
return is_permutation_inner (first1, last1, first2, last2, p);
return first1 == last1 && first2 == last2;
}
}
/// \endcond
#if __cplusplus >= 201103L
// Use the C++11 versions of is_permutation if it is available
using std::is_permutation; // Section 25.2.12
#else
/// \fn is_permutation ( ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 first2, BinaryPredicate p )
/// \brief Tests to see if 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 first1 The start of the input sequence
/// \param last1 One past the end of the input sequence
/// \param first2 The start of the second sequence
/// \param p The predicate to compare elements with
///
@ -67,19 +127,7 @@ bool is_permutation ( ForwardIterator1 first1, ForwardIterator1 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 boost::algorithm::detail::is_permutation_inner ( first1, last1, first2, last2, p );
}
return true;
@ -88,23 +136,84 @@ bool is_permutation ( ForwardIterator1 first1, ForwardIterator1 last1,
/// \fn is_permutation ( ForwardIterator1 first, ForwardIterator1 last, ForwardIterator2 first2 )
/// \brief Tests to see if 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 first1 The start of the input sequence
/// \param last2 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 )
bool is_permutation ( ForwardIterator1 first1, ForwardIterator1 last1, 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> ());
// Skip the common prefix (if any)
std::pair<ForwardIterator1, ForwardIterator2> eq = std::mismatch (first1, last1, first2 );
first1 = eq.first;
first2 = eq.second;
if ( first1 != last1 ) {
// Create last2
ForwardIterator2 last2 = first2;
std::advance ( last2, std::distance (first1, last1));
return boost::algorithm::detail::is_permutation_inner ( first1, last1, first2, last2,
std::equal_to<typename std::iterator_traits<ForwardIterator1>::value_type> ());
}
return true;
}
#endif
/// \fn is_permutation ( ForwardIterator1 first, ForwardIterator1 last,
/// ForwardIterator2 first2, ForwardIterator2 last2 )
/// \brief Tests to see if the sequence [first,last) is a permutation of the sequence starting at first2
///
/// \param first1 The start of the input sequence
/// \param last2 One past the end of the input sequence
/// \param first2 The start of the second sequence
/// \param last1 One past the end 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 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2 )
{
// 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::detail::is_permutation_tag (
first1, last1, first2, last2,
std::equal_to<typename std::iterator_traits<ForwardIterator1>::value_type> (),
typename std::iterator_traits<ForwardIterator1>::iterator_category (),
typename std::iterator_traits<ForwardIterator2>::iterator_category ());
}
/// \fn is_permutation ( ForwardIterator1 first, ForwardIterator1 last,
/// ForwardIterator2 first2, ForwardIterator2 last2,
/// BinaryPredicate p )
/// \brief Tests to see if the sequence [first,last) is a permutation of the sequence starting at first2
///
/// \param first1 The start of the input sequence
/// \param last1 One past the end of the input sequence
/// \param first2 The start of the second sequence
/// \param last2 One past the end of the second sequence
/// \param pred 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, ForwardIterator2 last2,
BinaryPredicate pred )
{
return boost::algorithm::detail::is_permutation_tag (
first1, last1, first2, last2, pred,
typename std::iterator_traits<ForwardIterator1>::iterator_category (),
typename std::iterator_traits<ForwardIterator2>::iterator_category ());
}
/// \fn is_permutation ( const Range &r, ForwardIterator first2 )
/// \brief Tests to see if the sequence [first,last) is a permutation of the sequence starting at first2
///