std::reverse

Defined in header `<algorithm>`
template< class BidirIt > void reverse( BidirIt first, BidirIt last );

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

Behaves as if applying std::iter_swap to every pair of iterators first+i, (last-i) - 1 for each non-negative i < (last-first)/2.

Parameters

first, last	-	the range of elements to reverse
Type requirements
- `BidirIt` must meet the requirements of `BidirectionalIterator`.
-The type of dereferenced `BidirIt` must meet the requirements of `Swappable`.

Return value

(none).

Possible implementation

template<class BidirIt>
void reverse(BidirIt first, BidirIt last)
{
    while ((first != last) && (first != --last)) {
        std::iter_swap(first++, last);
    }
}

Example

#include <vector>
#include <iostream>
#include <iterator>
#include <algorithm>
 
int main()
{
    std::vector<int> v({1,2,3});
    std::reverse(std::begin(v), std::end(v));
    std::cout << v[0] << v[1] << v[2] << '\n';
 
    int a[] = {4, 5, 6, 7};
    std::reverse(std::begin(a), std::end(a));
    std::cout << a[0] << a[1] << a[2] << a[3] << '\n';
}

Output:

321
7654

Complexity

linear in the distance between first and last.

reverse_copy	creates a copy of a range that is reversed (function template)
std::experimental::parallel::reverse (parallelism TS)	parallelized version of `std::reverse` (function template)