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[algorithm.search_n] Fix search_n's complexity violation.
According to document, at most last - first applications of the corresponding predicate, but (last - first) * count applications.
This commit is contained in:
Mitsuru Kariya
parent
b76e0aeb7f
commit
1a5d40d821
1 changed files with 112 additions and 10 deletions
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@ -11,11 +11,115 @@
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#include <iterator>
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#include <sprout/config.hpp>
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#include <sprout/iterator/operation.hpp>
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#include <sprout/iterator/value_iterator.hpp>
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#include <sprout/functional/equal_to.hpp>
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#include <sprout/algorithm/search.hpp>
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#include <sprout/tuple.hpp>
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#include <sprout/algorithm/find.hpp>
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#include <sprout/algorithm/find_if.hpp>
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namespace sprout {
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namespace detail {
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template<typename RandomAccessIterator, typename Size, typename T, typename BinaryPredicate>
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inline SPROUT_CONSTEXPR RandomAccessIterator
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search_n_impl_ra(
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RandomAccessIterator current, RandomAccessIterator last,
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Size count, T const& value, BinaryPredicate pred,
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typename std::iterator_traits<RandomAccessIterator>::difference_type len,
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RandomAccessIterator searched
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)
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{
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return sprout::distance(searched, current) >= count || searched == last ? searched
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: len == 1 ? pred(*current, value) ? searched
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: sprout::distance(current, last) > count ? sprout::next(current) : last
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: sprout::detail::search_n_impl_ra(
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current + len / 2, last, count, value, pred, len - len / 2,
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sprout::detail::search_n_impl_ra(
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current, last, count, value, pred, len / 2, searched
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)
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)
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;
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}
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template<typename RandomAccessIterator, typename Size, typename T, typename BinaryPredicate>
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inline SPROUT_CONSTEXPR typename std::enable_if<
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sprout::is_constant_distance_iterator<RandomAccessIterator>::value,
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RandomAccessIterator
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>::type
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search_n(
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RandomAccessIterator first, RandomAccessIterator last, Size count, T const& value, BinaryPredicate pred,
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std::random_access_iterator_tag*
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)
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{
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return sprout::distance(first, last) < count
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? last
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: sprout::detail::search_n_impl_ra(
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first, last, count, value, pred, sprout::distance(first, last), first
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)
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;
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}
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template<typename ForwardIterator, typename Size>
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inline SPROUT_CONSTEXPR ForwardIterator
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search_n_impl_check(
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sprout::tuple<ForwardIterator, ForwardIterator, Size> current,
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ForwardIterator last, Size count
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)
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{
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return sprout::tuples::get<2>(current) == count ? sprout::tuples::get<1>(current) : last;
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}
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template<typename ForwardIterator, typename Size, typename T, typename BinaryPredicate>
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inline SPROUT_CONSTEXPR sprout::tuple<ForwardIterator, ForwardIterator, Size>
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search_n_impl_1(
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sprout::tuple<ForwardIterator, ForwardIterator, Size> current,
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ForwardIterator last, Size count, T const& value, BinaryPredicate pred,
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typename std::iterator_traits<ForwardIterator>::difference_type n
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)
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{
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typedef sprout::tuple<ForwardIterator, ForwardIterator, Size> type;
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return sprout::tuples::get<2>(current) == count || sprout::tuples::get<0>(current) == last ? current
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: n == 1
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? pred(*sprout::tuples::get<0>(current), value)
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? type(sprout::next(sprout::tuples::get<0>(current)), sprout::tuples::get<1>(current), sprout::tuples::get<2>(current) + 1)
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: type(sprout::next(sprout::tuples::get<0>(current)), sprout::next(sprout::tuples::get<0>(current)), 0)
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: sprout::detail::search_n_impl_1(
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sprout::detail::search_n_impl_1(
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current,
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last, count, value, pred, n / 2
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),
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last, count, value, pred, n - n / 2
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)
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;
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}
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template<typename ForwardIterator, typename Size, typename T, typename BinaryPredicate>
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inline SPROUT_CONSTEXPR sprout::tuple<ForwardIterator, ForwardIterator, Size>
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search_n_impl(
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sprout::tuple<ForwardIterator, ForwardIterator, Size> current,
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ForwardIterator last, Size count, T const& value, BinaryPredicate pred,
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typename std::iterator_traits<ForwardIterator>::difference_type n
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)
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{
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return sprout::tuples::get<2>(current) == count || sprout::tuples::get<0>(current) == last ? current
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: sprout::detail::search_n_impl(
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sprout::detail::search_n_impl_1(
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current,
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last, count, value, pred, n
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),
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last, count, value, pred, n * 2
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)
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;
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}
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template<typename ForwardIterator, typename Size, typename T, typename BinaryPredicate>
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inline SPROUT_CONSTEXPR ForwardIterator
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search_n(
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ForwardIterator first, ForwardIterator last, Size count, T const& value, BinaryPredicate pred,
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std::forward_iterator_tag*
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)
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{
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typedef sprout::tuple<ForwardIterator, ForwardIterator, Size> type;
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return sprout::detail::search_n_impl_check(
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sprout::detail::search_n_impl(type(first, first, 0), last, count, value, pred, 1),
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last, count
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)
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;
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}
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}
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// 25.2.13 Search
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//
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// recursion depth:
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@ -24,19 +128,17 @@ namespace sprout {
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template<typename ForwardIterator, typename Size, typename T, typename BinaryPredicate>
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inline SPROUT_CONSTEXPR ForwardIterator
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search_n(ForwardIterator first, ForwardIterator last, Size count, T const& value, BinaryPredicate pred) {
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typedef sprout::value_iterator<T const&> iterator;
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typedef typename std::iterator_traits<iterator>::difference_type difference_type;
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return sprout::search(
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first, last,
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iterator(value, static_cast<difference_type>(count)), iterator(value, 0),
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pred
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);
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typedef typename std::iterator_traits<ForwardIterator>::iterator_category* category;
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return count == 0 ? last : count == 1 ? sprout::find_if(first, last, sprout::bind2nd(pred, value))
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: sprout::detail::search_n(first, last, count, value, pred, category());
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}
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template<typename ForwardIterator, typename Size, typename T>
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inline SPROUT_CONSTEXPR ForwardIterator
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search_n(ForwardIterator first, ForwardIterator last, Size count, T const& value) {
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return sprout::search_n(first, last, count, value, sprout::equal_to<>());
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typedef typename std::iterator_traits<ForwardIterator>::iterator_category* category;
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return count == 0 ? last : count == 1 ? sprout::find(first, last, value)
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: sprout::detail::search_n(first, last, count, value, sprout::equal_to<>(), category());
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}
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} // namespace sprout
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