std::ranges::is_sorted - 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 bool is_sorted( I first, S last, Comp comp = {}, Proj proj = {} ); | (1) | (since C++20) |
| 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 bool is_sorted( R&& r, Comp comp = {}, Proj proj = {} ); | (2) | (since C++20) |
Checks if the elements in range [first, last) 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 check if it is sorted |
|---|---|---|
| r | - | the range of elements to check if it is sorted |
| comp | - | comparison function to apply to the projected elements |
| proj | - | projection to apply to the elements |
[edit] Return value
true if the elements in the range are sorted according to comp.
[edit] Complexity
Linear in the distance between first and last.
[edit] Possible implementation
struct is_sorted_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 bool operator()(I first, S last, Comp comp = {}, Proj proj = {}) const { return ranges::is_sorted_until(first, last, comp, proj) == last; } template<ranges::forward_range R, class Proj = std::identity, std::indirect_strict_weak_order< std::projected<ranges::iterator_t, Proj>> Comp = ranges::less> constexpr bool 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_fn is_sorted;
[edit] Notes
ranges::is_sorted returns true for empty ranges and ranges of length one.
[edit] Example
#include #include #include #include #include int main() { namespace ranges = std::ranges; std::array digits {3, 1, 4, 1, 5}; ranges::copy(digits, std::ostream_iterator(std::cout, " ")); ranges::is_sorted(digits) ? std::cout << ": sorted\n" : std::cout << ": not sorted\n"; ranges::sort(digits); ranges::copy(digits, std::ostream_iterator(std::cout, " ")); ranges::is_sorted(ranges::begin(digits), ranges::end(digits)) ? std::cout << ": sorted\n" : std::cout << ": not sorted\n"; ranges::reverse(digits); ranges::copy(digits, std::ostream_iterator(std::cout, " ")); ranges::is_sorted(digits, ranges::greater {}) ? std::cout << ": sorted (with 'greater')\n" : std::cout << ": not sorted\n"; }
Output:
3 1 4 1 5 : not sorted 1 1 3 4 5 : sorted 5 4 3 1 1 : sorted (with 'greater')