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std::ranges::sort

From cppreference.com
< cpp‎ | algorithm‎ | ranges
 
 
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms: std::ranges::copy, std::ranges::sort, ...
Execution policies (C++17)
Non-modifying sequence operations
(C++11)(C++11)(C++11)
(C++17)
Modifying sequence operations
Operations on uninitialized storage
Partitioning operations
Sorting operations
(C++11)
Binary search operations
Set operations (on sorted ranges)
Heap operations
(C++11)
Minimum/maximum operations
(C++11)
(C++17)

Permutations
Numeric operations
C library
 
Constrained algorithms
Non-modifying sequence operations
Modifying sequence operations
Operations on uninitialized storage
Partitioning operations
Sorting operations
ranges::sort
Binary search operations
Set operations (on sorted ranges)
Heap operations
Minimum/maximum operations
Permutations
 
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 sortable<I, Comp, Proj>

constexpr I sort( I first, S last, Comp comp = {}, Proj proj = {} );
(1) (since C++20)
template< std::random_access_range R, class Comp = ranges::less,

          class Proj = std::identity >
requires sortable<ranges::iterator_t<R>, Comp, Proj>

constexpr ranges::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:

In practice, they may be implemented as function objects, or with special compiler extensions.

Contents

[edit] 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

[edit] Return value

An iterator equal to last.

[edit] Complexity

O(N·log(N)) comparisons and projections, where N = ranges::distance(first, last).

[edit] Possible implementation

[edit] Example

#include <algorithm>
#include <array>
#include <functional>
#include <iomanip>
#include <iostream>
 
void print(auto const& seq) {
    for (auto const& elem : seq) {
        std::cout << elem << ' ';
    }   
    std::cout << '\n';
}
 
struct Particle {
    std::string name; double mass; // MeV
    template<class Os> friend
    Os& operator<< (Os& os, Particle const& p) {
        return os << "\n" << 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;
 
    // sort using the default operator<
    ranges::sort(s);
    print(s);
 
    // sort using a standard library compare function object
    ranges::sort(s, ranges::greater());
    print(s);
 
    // sort using a custom function object
    struct {
        bool operator()(int a, int b) const {   
            return a < b;
        }   
    } customLess;
    ranges::sort(s.begin(), s.end(), customLess);
    print(s);
 
    // sort using a lambda expression 
    ranges::sort(s, [](int a, int b) {
        return a > b;   
    });
    print(s);
 
    // sort with projection
    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); //< sort by name
    print(particles);
    ranges::sort(particles, {}, &Particle::mass); //< sort by mass
    print(particles);
}

Output:

0 1 2 3 4 5 6 7 8 9 
9 8 7 6 5 4 3 2 1 0 
0 1 2 3 4 5 6 7 8 9 
9 8 7 6 5 4 3 2 1 0 
 
Electron : 0.511 
Muon     : 105.66 
Neutron  : 939.57 
Positron : 0.511 
Proton   : 938.27 
Tau      : 1776.86 
 
Electron : 0.511 
Positron : 0.511 
Muon     : 105.66 
Proton   : 938.27 
Neutron  : 939.57 
Tau      : 1776.86

[edit] See also

sorts the first N elements of a range
(niebloid) [edit]
sorts a range of elements while preserving order between equal elements
(niebloid) [edit]
sorts a range into ascending order
(function template) [edit]