std::ranges::is_sorted() algorithm
- od C++20
- Simplified
- Detailed
// (1)
constexpr bool
is_sorted( I first, S last, Comp comp = {}, Proj proj = {} );
// (2)
constexpr bool
is_sorted( R&& r, Comp comp = {}, Proj proj = {} );
The type of arguments are generic and have the following constraints:
I
-std::forward_iterator
S
-std::sentinel_for<I>
R
-std::ranges::forward_range
Comp
:- (1) -
std::indirect_strict_weak_order<std::projected<I, Proj>>
- (2) -
std::indirect_strict_weak_order<std::projected<ranges::iterator_t<R>, Proj>>
- (1) -
Proj
- (none)
The Proj
and Comp
template arguments have the following default types: std::identity
, ranges::less
for all overloads.
// (1)
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 = {} );
// (2)
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 = {} );
Checks if the elements in range [first
; last
) are sorted.
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.
Parameters
first last | The range of elements to examine. |
r | The range of elements to examine. |
comp | Comparison function to apply to the projected elemenets. |
proj | The projection to apply to the elements. |
Return value
true
if the elements in the range are sorted according to comp
(also for empty ranges and ranges of length one).
Complexity
Linear in the distance between first
and last
.
Exceptions
(none)
Possible implementation
is_sorted(1) and is_sorted(2)
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;
Examples
#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";
}
3 1 4 1 5 : not sorted
1 1 3 4 5 : sorted
5 4 3 1 1 : sorted (with 'greater')
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