Std::iter_swap (3) Linux Manual Page

std::iter_swap – std::iter_swap

Synopsis

Defined in header<algorithm>

    template <class ForwardIt1, class ForwardIt2>
    (until C++ 20)

        void iter_swap(ForwardIt1 a, ForwardIt2 b);

template <class ForwardIt1, class ForwardIt2>
(since C++ 20)

    constexpr void iter_swap(ForwardIt1 a, ForwardIt2 b);

Swaps the values of the elements the given iterators are pointing to.

Parameters

a, b – iterators to the elements to swap

Type requirements

–
ForwardIt1, ForwardIt2 must meet the requirements of LegacyForwardIterator.
–
*a, *b must meet the requirements of Swappable.

Return value

(none)

Complexity

constant

Possible implementation

  template<class ForwardIt1, class ForwardIt2>
  constexpr void iter_swap(ForwardIt1 a, ForwardIt2 b) // constexpr since C++20
  {
     using std::swap;
     swap(*a, *b);
  }

Example

The following is an implementation of selection sort in C++
// Run this code

#include <random>

#include <vector>

#include <iostream>

#include <algorithm>

#include <functional>
template <class ForwardIt>

void selection_sort(ForwardIt begin, ForwardIt end)

{
    for (ForwardIt i = begin; i != end; ++i)
        std::iter_swap(i, std::min_element(i, end));
}
int main()

{
    std::random_device rd;
    std::mt19937 gen(rd());
    std::uniform_int_distribution<> dist(-10, 10);
    std::vector<int> v;
    generate_n(back_inserter(v), 20, bind(dist, gen));
    std::cout << "Before sort: ";
    for (auto e : v)
        std::cout << e << " ";
    selection_sort(v.begin(), v.end());
    std::cout << "\nAfter sort: ";
    for (auto e : v)
        std::cout << e << " ";
    std::cout << '\n';
}

Output:

Before sort: -7 6 2 4 -1 6 -9 -1 2 -5 10 -9 -5 -3 -5 -3 6 6 1 8
After sort: -9 -9 -7 -5 -5 -5 -3 -3 -1 -1 1 2 2 4 6 6 6 6 8 10

std::iter_swap (3) Linux Manual Page