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std::ranges...orted_until(3) C++ Standard Libary std::ranges...orted_until(3) NAME std::ranges::is_sorted_until - std::ranges::is_sorted_until Synopsis Defined in header <algorithm> Call signature template< std::forward_iterator I, std::sentinel_for<I> S, class Proj = std::identity, std::indirect_strict_weak_order<std::projected<I, Proj>> Comp = (1) (since ranges::less > C++20) constexpr I is_sorted_until( I first, S last, Comp comp = {}, Proj proj = {} ); template< std::forward_range R, class Proj = std::identity, std::indirect_strict_weak_order< (since std::projected<ranges::iterator_t<R>, Proj>> Comp = ranges::less > (2) C++20) constexpr ranges::borrowed_iterator_t<R> is_sorted_until( R&& r, Comp comp = {}, Proj proj = {} ); Examines the range [first, last) and finds the largest range begin- ning at first in which the elements are sorted in non-descending order. A sequence is sorted with respect to a comparator comp if for any iterator it pointing to the sequence and any non-negative integer n such that it + n is a valid iterator pointing to an element of the sequence, std::invoke(comp, std::invoke(proj, *(it + n)), std::invoke(proj, *it)) evaluates to false. 1) Elements are compared using the given binary comparison function comp. 2) Same as (1), but uses r as the source range, as if using ranges::begin(r) as first and ranges::end(r) as last. The function-like entities described on this page are niebloids, that is: * Explicit template argument lists may not be specified when call- ing any of them. * None of them is visible to argument-dependent lookup. * When one of them is found by normal unqualified lookup for the name to the left of the function-call operator, it inhibits argument-dependent lookup. In practice, they may be implemented as function objects, or with special compiler extensions. Parameters first, last - iterator-sentinel defining the range to find its sorted upper bound r - the range to find its sorted upper bound comp - comparison function to apply to the projected elements proj - projection to apply to the elements Return value The upper bound of the largest range beginning at first in which the elements are sorted in non-descending order. That is, the last iterator it for which range [first, it) is sorted. Complexity Linear in the distance between first and last. Possible implementation struct is_sorted_until_fn { template<std::forward_iterator I, std::sentinel_for<I> S, class Proj = std::identity, std::indirect_strict_weak_order<std::projected<I, Proj>> Comp = ranges::less> constexpr I operator()(I first, S last, Comp comp = {}, Proj proj = {}) const { if (first == last) { return first; } auto next = first; while (++next != last) { if (std::invoke(comp, std::invoke(proj, *next), std::in- voke(proj, *first))) { return next; } first = next; } return first; } template< ranges::forward_range R, class Proj = std::identity, std::indirect_strict_weak_order< std::projected<ranges::iterator_t<R>, Proj>> Comp = ranges::less > constexpr ranges::borrowed_iterator_t<R> operator()( R&& r, Comp comp = {}, Proj proj = {} ) const { return (*this)(ranges::begin(r), ranges::end(r), std::ref(comp), std::ref(proj)); } }; inline constexpr is_sorted_until_fn is_sorted_until; Notes ranges::is_sorted_until returns an iterator equal to last for empty ranges and ranges of length one. Example // Run this code #include <algorithm> #include <iostream> #include <iterator> #include <random> int main() { std::random_device rd; std::mt19937 g{rd()}; std::array nums {3, 1, 4, 1, 5, 9}; constexpr int min_sorted_size = 4; int sorted_size = 0; do { std::ranges::shuffle(nums, g); const auto sorted_end = std::ranges::is_sorted_until(nums); sorted_size = std::ranges::distance(nums.begin(), sorted_end); std::ranges::copy(nums, std::ostream_iterator<int>(std::cout, " ")); std::cout << " : " << sorted_size << " leading sorted ele- ment(s)\n"; } while (sorted_size < min_sorted_size); } Possible output: 4 1 9 5 1 3 : 1 leading sorted element(s) 4 5 9 3 1 1 : 3 leading sorted element(s) 9 3 1 4 5 1 : 1 leading sorted element(s) 1 3 5 4 1 9 : 3 leading sorted element(s) 5 9 1 1 3 4 : 2 leading sorted element(s) 4 9 1 5 1 3 : 2 leading sorted element(s) 1 1 4 9 5 3 : 4 leading sorted element(s) See also ranges::is_sorted checks whether a range is sorted into ascending order (C++20) (niebloid) is_sorted_until finds the largest sorted subrange (C++11) (function template) http://cppreference.com 2022.07.31 std::ranges...orted_until(3)
NAME | Synopsis | Parameters | Return value | Complexity | Possible implementation | Notes | Example | Possible output: | See also
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