# std::sort

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< cpp‎ | algorithm

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

Run this code

    #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

### See also

partial_sort | sorts the first N elements of a range (function template)
stable_sort | sorts a range of elements while preserving order between equal elements (function template)

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