std::sort

Learn to sort with std::sort.

std::sort

std::sort sorts a range in place. It takes two iterators: std::sort(v.begin(), v.end()). By default it sorts in ascending order (small to large). It is defined in <algorithm>.

Sorting requires random access iterators; that is why it works on std::vector and std::array but not on std::list. The sort is efficient (usually O(n log n)). It modifies the container directly and does not create a new one. That is why it is called an 'in-place' sort.

Descending sort

To sort descending, pass std::greater<int>() as the third parameter: std::sort(v.begin(), v.end(), std::greater<int>());. This uses the > operator to sort large to small.

std::greater is a functor defined in <functional>. A functor is a class with operator(); it can be called like a function. At an advanced level you can write your own functors or use lambdas, but ready-made functors like std::greater cover most cases.

Exercise Sort and print a vector

Sort the vector v = {5, 2, 8, 1, 9} in ascending order with std::sort. Then print each element followed by a space in a for loop.

Show example solution

#include <iostream>
#include <vector>
#include <algorithm>

int main() {
    std::vector<int> v = {5, 2, 8, 1, 9};
    std::sort(v.begin(), v.end());
    for (int x : v) {
        std::cout << x << " ";
    }
    return 0;
}

Test yourself

How does std::sort order by default?
```
std::sort(v.begin(), v.end());
```
- Descending (large to small)
- Randomly
- Reversed
- Ascending (small to large)
Show answer

Ascending (small to large) — The default is ascending order.

Complete the sort call

std::____(v.begin(), v.end());

Show answer

std::sort(v.begin(), v.end());

Match each piece to its role

std::sort(begin, end)

Ascending sort
std::greater<int>()

Descending sort
v.begin()

Range start
v.end()

Range end

Next lesson: std::find

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