std::ranges::sort
Defined in header <algorithm> |
||
|---|---|---|
| Call signature | ||
template< std::random_access_iterator I, std::sentinel_for<I> S,
class Comp = ranges::less, class Proj = std::identity >
requires std::sortable<I, Comp, Proj>
constexpr I
sort( I first, S last, Comp comp = {}, Proj proj = {} ); |
(1) | (since C++20) |
template< ranges::random_access_range R, class Comp = ranges::less,
class Proj = std::identity >
requires std::sortable<ranges::iterator_t<R>, Comp, Proj>
constexpr ranges::borrowed_iterator_t<R>
sort( R&& r, Comp comp = {}, Proj proj = {} ); |
(2) | (since C++20) |
Sorts the elements in the range [first, last) in non-descending order. The order of equivalent elements is not guaranteed to be preserved.
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 calling 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 sort |
| r | - | the range to sort |
| comp | - | comparison to apply to the projected elements |
| proj | - | projection to apply to the elements |
Return value
An iterator equal to last.
Complexity
\(\scriptsize \mathcal{O}(N\cdot\log{(N)})\)𝓞(N·log(N)) comparisons and projections, where N = ranges::distance(first, last).
Possible implementation
Note that typical implementations use introsort. See also the implementation in MSVC STL and libstdc++.
struct sort_fn {
template< std::random_access_iterator I, std::sentinel_for<I> S,
class Comp = ranges::less, class Proj = std::identity >
requires std::sortable<I, Comp, Proj>
constexpr I
operator()( I first, S last, Comp comp = {}, Proj proj = {} ) const {
if (first == last)
return first;
I last_iter = ranges::next(first, last);
ranges::make_heap(first, last_iter, std::ref(comp), std::ref(proj));
ranges::sort_heap(first, last_iter, std::ref(comp), std::ref(proj));
return last_iter;
}
template< ranges::random_access_range R, class Comp = ranges::less,
class Proj = std::identity >
requires std::sortable<ranges::iterator_t<R>, Comp, Proj>
constexpr ranges::borrowed_iterator_t<R>
operator()( R&& r, Comp comp = {}, Proj proj = {} ) const {
return (*this)(ranges::begin(r), ranges::end(r), std::move(comp), std::move(proj));
}
};
inline constexpr sort_fn sort{};
|
Example
#include <algorithm>
#include <array>
#include <functional>
#include <iomanip>
#include <iostream>
void print(auto comment, auto const& seq, char term = ' ') {
for (std::cout << comment << '\n'; auto const& elem : seq)
std::cout << elem << term;
std::cout << '\n';
}
struct Particle {
std::string name; double mass; // MeV
template<class Os> friend
Os& operator<< (Os& os, Particle const& p) {
return os << std::left << std::setw(8) << p.name << " : " << p.mass << ' ';
}
};
int main()
{
std::array s {5, 7, 4, 2, 8, 6, 1, 9, 0, 3};
namespace ranges = std::ranges;
ranges::sort(s);
print("Sort using the default operator<", s);
ranges::sort(s, ranges::greater());
print("Sort using a standard library compare function object", s);
struct {
bool operator()(int a, int b) const { return a < b; }
} customLess;
ranges::sort(s.begin(), s.end(), customLess);
print("Sort using a custom function object", s);
ranges::sort(s, [](int a, int b) { return a > b; });
print("Sort using a lambda expression", s);
Particle particles[] {
{"Electron", 0.511}, {"Muon", 105.66}, {"Tau", 1776.86},
{"Positron", 0.511}, {"Proton", 938.27}, {"Neutron", 939.57},
};
ranges::sort(particles, {}, &Particle::name);
print("\nSort by name using a projection", particles, '\n');
ranges::sort(particles, {}, &Particle::mass);
print("Sort by mass using a projection", particles, '\n');
}
Output:
Sort using the default operator< 0 1 2 3 4 5 6 7 8 9 Sort using a standard library compare function object 9 8 7 6 5 4 3 2 1 0 Sort using a custom function object 0 1 2 3 4 5 6 7 8 9 Sort using a lambda expression 9 8 7 6 5 4 3 2 1 0 Sort by name using a projection Electron : 0.511 Muon : 105.66 Neutron : 939.57 Positron : 0.511 Proton : 938.27 Tau : 1776.86 Sort by mass using a projection Electron : 0.511 Positron : 0.511 Muon : 105.66 Proton : 938.27 Neutron : 939.57 Tau : 1776.86
See also
|
(C++20)
|
sorts the first N elements of a range (niebloid) |
|
(C++20)
|
sorts a range of elements while preserving order between equal elements (niebloid) |
|
(C++20)
|
divides a range of elements into two groups (niebloid) |
| sorts a range into ascending order (function template) |
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