std::ranges::is_sorted
From cppreference.com
| Defined in header <algorithm>
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| Call signature |
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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.
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 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.
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 |
Return value
true if the elements in the range are sorted according to comp.
Complexity
Linear in the distance between first and last.
Possible implementation
struct is_sorted_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 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<R>, 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;
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Notes
ranges::is_sorted returns true for empty ranges and ranges of length one.
Example
Run this code
#include <algorithm>
#include <array>
#include <functional>
#include <iostream>
#include <iterator>
int main()
{
namespace ranges = std::ranges;
std::array digits {3, 1, 4, 1, 5};
ranges::copy(digits, std::ostream_iterator<int>(std::cout, " "));
ranges::is_sorted(digits)
? std::cout << ": sorted\n"
: std::cout << ": not sorted\n";
ranges::sort(digits);
ranges::copy(digits, std::ostream_iterator<int>(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<int>(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')
See also
(C++20) |
finds the largest sorted subrange (algorithm function object) |
(C++11) |
checks whether a range is sorted into ascending order (function template) |