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std::sort

Defined in header `<algorithm>`
	(1)
template< class RandomIt > void sort( RandomIt first, RandomIt last );		(until C++20)
template< class RandomIt > constexpr void sort( RandomIt first, RandomIt last );		(since C++20)
template< class ExecutionPolicy, class RandomIt > void sort( ExecutionPolicy&& policy, RandomIt first, RandomIt last );	(2)	(since C++17)
	(3)
template< class RandomIt, class Compare > void sort( RandomIt first, RandomIt last, Compare comp );		(until C++20)
template< class RandomIt, class Compare > constexpr void sort( RandomIt first, RandomIt last, Compare comp );		(since C++20)
template< class ExecutionPolicy, class RandomIt, class Compare > void sort( ExecutionPolicy&& policy, RandomIt first, RandomIt last, Compare comp );	(4)	(since C++17)

Sorts the elements in the range [first, last) in ascending order. The order of equal elements is not guaranteed to be preserved.

1) Elements are compared using operator<.

3) Elements are compared using the given binary comparison function comp.

2,4) Same as (1,3), but executed according to policy. These overloads do not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true

Parameters

first, last	-	the range of elements to sort
policy	-	the execution policy to use. See execution policy for details.
comp	-	comparison function object (i.e. an object that satisfies the requirements of Compare) which returns `true` if the first argument is less than (i.e. is ordered before) the second. The signature of the comparison function should be equivalent to the following: `bool cmp(const Type1 &a, const Type2 &b);` While the signature does not need to have `const &`, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) `Type1` and `Type2` regardless of value category (thus, `Type1 &` is not allowed, nor is `Type1` unless for `Type1` a move is equivalent to a copy (since C++11)). The types `Type1` and `Type2` must be such that an object of type `RandomIt` can be dereferenced and then implicitly converted to both of them.
Type requirements
-`RandomIt` must meet the requirements of ValueSwappable and LegacyRandomAccessIterator.
-The type of dereferenced `RandomIt` must meet the requirements of MoveAssignable and MoveConstructible.
-`Compare` must meet the requirements of Compare.

Return value

(none).

Complexity

O(N·log(N)), where `N = std::distance(first, last)` comparisons on average.	(until C++11)
O(N·log(N)), where `N = std::distance(first, last)` comparisons.	(since C++11)

Exceptions

The overloads with a template parameter named ExecutionPolicy report errors as follows:

If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Example

#include <algorithm>
#include <functional>
#include <array>
#include <iostream>
 
int main()
{
    std::array<int, 10> s = {5, 7, 4, 2, 8, 6, 1, 9, 0, 3}; 
 
    // sort using the default operator<
    std::sort(s.begin(), s.end());
    for (auto a : s) {
        std::cout << a << " ";
    }   
    std::cout << '\n';
 
    // sort using a standard library compare function object
    std::sort(s.begin(), s.end(), std::greater<int>());
    for (auto a : s) {
        std::cout << a << " ";
    }   
    std::cout << '\n';
 
    // sort using a custom function object
    struct {
        bool operator()(int a, int b) const
        {   
            return a < b;
        }   
    } customLess;
    std::sort(s.begin(), s.end(), customLess);
    for (auto a : s) {
        std::cout << a << " ";
    }   
    std::cout << '\n';
 
    // sort using a lambda expression 
    std::sort(s.begin(), s.end(), [](int a, int b) {
        return a > b;   
    });
    for (auto a : s) {
        std::cout << a << " ";
    } 
    std::cout << '\n';
}

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