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Showing content from https://en.cppreference.com/w/cpp/language/../header/../iterator/../algorithm/ranges/reverse.html below:

std::ranges::reverse - cppreference.com

1) Reverses the order of the elements in the range [first, last).

Behaves as if applying

ranges::iter_swap

to every pair of iterators

first + i, last - i - 1

for each integer

i

, where

0 â¤ i < (last - first) / 2

The function-like entities described on this page are algorithm function objects (informally known as niebloids), that is:

Explicit template argument lists cannot be specified when calling any of them.
None of them are visible to argument-dependent lookup.
When any of them are found by normal unqualified lookup as the name to the left of the function-call operator, argument-dependent lookup is inhibited.

[edit] Parameters first, last - the iterator-sentinel pair defining the range of elements to reverse r - the range of elements to reverse [edit] Return value

An iterator equal to last.

[edit] Complexity

Exactly (last - first) / 2 swaps.

[edit] Notes

Implementations (e.g. MSVC STL) may enable vectorization when the iterator type models contiguous_iterator and swapping its value type calls neither non-trivial special member function nor ADL-found swap.

[edit] Possible implementation

See also implementations in libstdc++ and MSVC STL.

[edit] Example

#include <algorithm>
#include <array>
#include <iostream>
#include <string>
 
int main()
{
    std::string s {"ABCDEF"};
    std::cout << s << " â ";
    std::ranges::reverse(s.begin(), s.end());
    std::cout << s << " â ";
    std::ranges::reverse(s);
    std::cout << s << " â ";
 
    std::array a {1, 2, 3, 4, 5};
    for (auto e : a)
        std::cout << e << ' ';
    std::cout << "â ";
    std::ranges::reverse(a);
    for (auto e : a)
        std::cout << e << ' ';
    std::cout << '\n';
}

Output:

ABCDEF â FEDCBA â ABCDEF â 1 2 3 4 5 â 5 4 3 2 1

[edit] See also

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