📄 stl_algo.h
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if ((__first == __middle) || (__last == __middle)) return; std::__reverse(__first, __middle, bidirectional_iterator_tag()); std::__reverse(__middle, __last, bidirectional_iterator_tag()); while (__first != __middle && __middle != __last) swap(*__first++, *--__last); if (__first == __middle) std::__reverse(__middle, __last, bidirectional_iterator_tag()); else std::__reverse(__first, __middle, bidirectional_iterator_tag()); } /** * @if maint * This is a helper function for the rotate algorithm. * @endif */ template<typename _RandomAccessIterator> void __rotate(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last, random_access_iterator_tag) { // concept requirements __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept< _RandomAccessIterator>) if ((__first == __middle) || (__last == __middle)) return; typedef typename iterator_traits<_RandomAccessIterator>::difference_type _Distance; typedef typename iterator_traits<_RandomAccessIterator>::value_type _ValueType; const _Distance __n = __last - __first; const _Distance __k = __middle - __first; const _Distance __l = __n - __k; if (__k == __l) { std::swap_ranges(__first, __middle, __middle); return; } const _Distance __d = __gcd(__n, __k); for (_Distance __i = 0; __i < __d; __i++) { const _ValueType __tmp = *__first; _RandomAccessIterator __p = __first; if (__k < __l) { for (_Distance __j = 0; __j < __l / __d; __j++) { if (__p > __first + __l) { *__p = *(__p - __l); __p -= __l; } *__p = *(__p + __k); __p += __k; } } else { for (_Distance __j = 0; __j < __k / __d - 1; __j ++) { if (__p < __last - __k) { *__p = *(__p + __k); __p += __k; } *__p = * (__p - __l); __p -= __l; } } *__p = __tmp; ++__first; } } /** * @brief Rotate the elements of a sequence. * @param first A forward iterator. * @param middle A forward iterator. * @param last A forward iterator. * @return Nothing. * * Rotates the elements of the range @p [first,last) by @p (middle-first) * positions so that the element at @p middle is moved to @p first, the * element at @p middle+1 is moved to @first+1 and so on for each element * in the range @p [first,last). * * This effectively swaps the ranges @p [first,middle) and * @p [middle,last). * * Performs @p *(first+(n+(last-middle))%(last-first))=*(first+n) for * each @p n in the range @p [0,last-first). */ template<typename _ForwardIterator> inline void rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last) { // concept requirements __glibcxx_function_requires(_Mutable_ForwardIteratorConcept< _ForwardIterator>) __glibcxx_requires_valid_range(__first, __middle); __glibcxx_requires_valid_range(__middle, __last); typedef typename iterator_traits<_ForwardIterator>::iterator_category _IterType; std::__rotate(__first, __middle, __last, _IterType()); } /** * @brief Copy a sequence, rotating its elements. * @param first A forward iterator. * @param middle A forward iterator. * @param last A forward iterator. * @param result An output iterator. * @return An iterator designating the end of the resulting sequence. * * Copies the elements of the range @p [first,last) to the range * beginning at @result, rotating the copied elements by @p (middle-first) * positions so that the element at @p middle is moved to @p result, the * element at @p middle+1 is moved to @result+1 and so on for each element * in the range @p [first,last). * * Performs @p *(result+(n+(last-middle))%(last-first))=*(first+n) for * each @p n in the range @p [0,last-first). */ template<typename _ForwardIterator, typename _OutputIterator> _OutputIterator rotate_copy(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last, _OutputIterator __result) { // concept requirements __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>) __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator, typename iterator_traits<_ForwardIterator>::value_type>) __glibcxx_requires_valid_range(__first, __middle); __glibcxx_requires_valid_range(__middle, __last); return std::copy(__first, __middle, copy(__middle, __last, __result)); } /** * @brief Randomly shuffle the elements of a sequence. * @param first A forward iterator. * @param last A forward iterator. * @return Nothing. * * Reorder the elements in the range @p [first,last) using a random * distribution, so that every possible ordering of the sequence is * equally likely. */ template<typename _RandomAccessIterator> inline void random_shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last) { // concept requirements __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept< _RandomAccessIterator>) __glibcxx_requires_valid_range(__first, __last); if (__first != __last) for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i) std::iter_swap(__i, __first + (std::rand() % ((__i - __first) + 1))); } /** * @brief Shuffle the elements of a sequence using a random number * generator. * @param first A forward iterator. * @param last A forward iterator. * @param rand The RNG functor or function. * @return Nothing. * * Reorders the elements in the range @p [first,last) using @p rand to * provide a random distribution. Calling @p rand(N) for a positive * integer @p N should return a randomly chosen integer from the * range [0,N). */ template<typename _RandomAccessIterator, typename _RandomNumberGenerator> void random_shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last, _RandomNumberGenerator& __rand) { // concept requirements __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept< _RandomAccessIterator>) __glibcxx_requires_valid_range(__first, __last); if (__first == __last) return; for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i) std::iter_swap(__i, __first + __rand((__i - __first) + 1)); } /** * @if maint * This is a helper function... * @endif */ template<typename _ForwardIterator, typename _Predicate> _ForwardIterator __partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred, forward_iterator_tag) { if (__first == __last) return __first; while (__pred(*__first)) if (++__first == __last) return __first; _ForwardIterator __next = __first; while (++__next != __last) if (__pred(*__next)) { swap(*__first, *__next); ++__first; } return __first; } /** * @if maint * This is a helper function... * @endif */ template<typename _BidirectionalIterator, typename _Predicate> _BidirectionalIterator __partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred, bidirectional_iterator_tag) { while (true) { while (true) if (__first == __last) return __first; else if (__pred(*__first)) ++__first; else break; --__last; while (true) if (__first == __last) return __first; else if (!__pred(*__last)) --__last; else break; std::iter_swap(__first, __last); ++__first; } } /** * @brief Move elements for which a predicate is true to the beginning * of a sequence. * @param first A forward iterator. * @param last A forward iterator. * @param pred A predicate functor. * @return An iterator @p middle such that @p pred(i) is true for each * iterator @p i in the range @p [first,middle) and false for each @p i * in the range @p [middle,last). * * @p pred must not modify its operand. @p partition() does not preserve * the relative ordering of elements in each group, use * @p stable_partition() if this is needed. */ template<typename _ForwardIterator, typename _Predicate> inline _ForwardIterator partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) { // concept requirements __glibcxx_function_requires(_Mutable_ForwardIteratorConcept< _ForwardIterator>) __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate, typename iterator_traits<_ForwardIterator>::value_type>) __glibcxx_requires_valid_range(__first, __last); return std::__partition(__first, __last, __pred, std::__iterator_category(__first)); } /** * @if maint * This is a helper function... * @endif */ template<typename _ForwardIterator, typename _Predicate, typename _Distance> _ForwardIterator __inplace_stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred, _Distance __len) { if (__len == 1) return __pred(*__first) ? __last : __first; _ForwardIterator __middle = __first; std::advance(__middle, __len / 2); _ForwardIterator __begin = std::__inplace_stable_partition(__first, __middle, __pred, __len / 2); _ForwardIterator __end = std::__inplace_stable_partition(__middle, __last, __pred, __len - __len / 2); std::rotate(__begin, __middle, __end); std::advance(__begin, std::distance(__middle, __end)); return __begin; } /** * @if maint * This is a helper function... * @endif */ template<typename _ForwardIterator, typename _Pointer, typename _Predicate, typename _Distance> _ForwardIterator __stable_partition_adaptive(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred, _Distance __len, _Pointer __buffer, _Distance __buffer_size) { if (__len <= __buffer_size) { _ForwardIterator __result1 = __first; _Pointer __result2 = __buffer; for ( ; __first != __last ; ++__first) if (__pred(*__first)) { *__result1 = *__first; ++__result1; } else { *__result2 = *__first; ++__result2; } std::copy(__buffer, __result2, __result1); return __result1; } else { _ForwardIterator __middle = __first; std::advance(__middle, __len / 2); _ForwardIterator __begin = std::__stable_partition_adaptive(__first, __middle, __pred, __len / 2, __buffer, __buffer_size); _ForwardIterator __end = std::__stable_partition_adaptive(__middle, __last, __pred, __len - __len / 2, __buffer, __buffer_size); std::rotate(__begin, __middle, __end); std::advance(__begin, std::distance(__middle, __end)); return __begin; } } /** * @brief Move elements for which a predicate is true to the beginning * of a sequence, preserving relative ordering. * @param first A forward iterator. * @param last A forward iterator. * @param pred A predicate functor. * @return An iterator @p middle such that @p pred(i) is true for each
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