std::ranges::is_sorted_until - cppreference.com (original) (raw)
| Defined in header | ||
|---|---|---|
| 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 = ranges::less > constexpr I is_sorted_until( I first, S last, Comp comp = {}, Proj proj = {} ); | (1) | (since C++20) |
| template< std::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> is_sorted_until( R&& r, Comp comp = {}, Proj proj = {} ); | (2) | (since C++20) |
Examines the range [first, last) and finds the largest range beginning 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.
Elements are compared using the given binary comparison function comp.
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 algorithm function objects (informally known as niebloids), that is:
- Explicit template argument lists cannot be specified when calling any of them.
- None of them are visible to argument-dependent lookup.
- When any of them are found by normal unqualified lookup as the name to the left of the function-call operator, argument-dependent lookup is inhibited.
Contents
[edit] Parameters
| first, last | - | the iterator-sentinel pair defining the range of elements 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 |
[edit] 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.
[edit] Complexity
Linear in the distance between first and last.
[edit] Possible implementation
struct is_sorted_until_fn { template<std::forward_iterator I, std::sentinel_for 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; for (auto next = first; ++next != last; first = next) if (std::invoke(comp, std::invoke(proj, *next), std::invoke(proj, *first))) return next; return first; } template<ranges::forward_range R, class Proj = std::identity, std::indirect_strict_weak_order< std::projected<ranges::iterator_t, Proj>> Comp = ranges::less> constexpr ranges::borrowed_iterator_t 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;
[edit] Notes
ranges::is_sorted_until returns an iterator equal to last for empty ranges and ranges of length one.
[edit] Example
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)