notes/OJ notes/pages/cpp_std_sort.md

# Sort

#### 2022-06-11

---

##### Algorithms:

#algorithm #sort

##### Difficulty:

#CS_analysis #difficulty_easy

##### Related problems:

##### Links:

- [cpp reference](https://en.cppreference.com/w/cpp/algorithm/sort)

---

### What is Sort?

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

The default Compare function is less: `<`

### Example

```cpp
#include <algorithm>
#include <functional>
#include <array>
#include <iostream>
#include <string_view>

int main()
{
    std::array<int, 10> s = {5, 7, 4, 2, 8, 6, 1, 9, 0, 3};

    auto print = [&s](std::string_view const rem) {
        for (auto a : s) {
            std::cout << a << ' ';
        }
        std::cout << ": " << rem << '\n';
    };

    std::sort(s.begin(), s.end());
    print("sorted with the default operator<");

    std::sort(s.begin(), s.end(), std::greater<int>());
    print("sorted with the standard library compare function object");

    struct {
        bool operator()(int a, int b) const { return a < b; }
    } customLess;
    std::sort(s.begin(), s.end(), customLess);
    print("sorted with a custom function object");

    std::sort(s.begin(), s.end(), [](int a, int b) {
        return a > b;
    });
    print("sorted with a lambda expression");
}
```