mirror of
https://github.com/bolero-MURAKAMI/Sprout.git
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114 lines
4.2 KiB
C++
114 lines
4.2 KiB
C++
/*=============================================================================
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Copyright (c) 2011-2019 Bolero MURAKAMI
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https://github.com/bolero-MURAKAMI/Sprout
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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#ifndef SPROUT_ALGORITHM_COUNT_HPP
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#define SPROUT_ALGORITHM_COUNT_HPP
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#include <iterator>
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#include <type_traits>
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#include <sprout/config.hpp>
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#include <sprout/iterator/operation.hpp>
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#include <sprout/iterator/type_traits/category.hpp>
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#include <sprout/utility/pair/pair.hpp>
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namespace sprout {
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namespace detail {
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template<typename RandomAccessIterator, typename T>
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inline SPROUT_CONSTEXPR typename std::iterator_traits<RandomAccessIterator>::difference_type
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count_impl_ra(
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RandomAccessIterator const& first, T const& value,
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typename std::iterator_traits<RandomAccessIterator>::difference_type size
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)
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{
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return size == 1 ? (*first == value ? 1 : 0)
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: sprout::detail::count_impl_ra(
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first, value,
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size / 2
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)
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+ sprout::detail::count_impl_ra(
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sprout::next(first, size / 2), value,
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size - size / 2
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)
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;
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}
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template<typename RandomAccessIterator, typename T>
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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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typename std::iterator_traits<RandomAccessIterator>::difference_type
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>::type
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count(
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RandomAccessIterator const& first, RandomAccessIterator const& last, T const& value,
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std::random_access_iterator_tag*
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)
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{
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return first == last ? 0
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: sprout::detail::count_impl_ra(first, value, sprout::distance(first, last))
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;
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}
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template<typename InputIterator, typename T>
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inline SPROUT_CONSTEXPR sprout::pair<InputIterator, typename std::iterator_traits<InputIterator>::difference_type>
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count_impl_1(
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sprout::pair<InputIterator, typename std::iterator_traits<InputIterator>::difference_type> const& current,
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InputIterator const& last, T const& value, typename std::iterator_traits<InputIterator>::difference_type n
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)
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{
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typedef sprout::pair<InputIterator, typename std::iterator_traits<InputIterator>::difference_type> type;
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return current.first == last ? current
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: n == 1 ? type(sprout::next(current.first), current.second + (*current.first == value ? 1 : 0))
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: sprout::detail::count_impl_1(
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sprout::detail::count_impl_1(
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current,
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last, value, n / 2
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),
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last, value, n - n / 2
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)
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;
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}
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template<typename InputIterator, typename T>
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inline SPROUT_CONSTEXPR sprout::pair<InputIterator, typename std::iterator_traits<InputIterator>::difference_type>
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count_impl(
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sprout::pair<InputIterator, typename std::iterator_traits<InputIterator>::difference_type> const& current,
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InputIterator const& last, T const& value, typename std::iterator_traits<InputIterator>::difference_type n
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)
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{
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return current.first == last ? current
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: sprout::detail::count_impl(
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sprout::detail::count_impl_1(
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current,
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last, value, n
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),
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last, value, n * 2
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)
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;
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}
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template<typename InputIterator, typename T>
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inline SPROUT_CONSTEXPR typename std::iterator_traits<InputIterator>::difference_type
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count(
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InputIterator const& first, InputIterator const& last, T const& value,
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std::input_iterator_tag*
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)
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{
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typedef sprout::pair<InputIterator, typename std::iterator_traits<InputIterator>::difference_type> type;
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return sprout::detail::count_impl(type(first, 0), last, value, 1).second;
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}
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} // namespace detail
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// 25.2.9 Count
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//
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// recursion depth:
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// O(log N)
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//
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template<typename InputIterator, typename T>
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inline SPROUT_CONSTEXPR typename std::iterator_traits<InputIterator>::difference_type
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count(InputIterator first, InputIterator last, T const& value) {
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typedef typename std::iterator_traits<InputIterator>::iterator_category* category;
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return sprout::detail::count(first, last, value, category());
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}
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} // namespace sprout
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#endif // #ifndef SPROUT_ALGORITHM_COUNT_HPP
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