std::reverse_copy

Defined in header `<algorithm>`
	(1)
template< class BidirIt, class OutputIt > OutputIt reverse_copy( BidirIt first, BidirIt last, OutputIt d_first );			(until C++20)
template< class BidirIt, class OutputIt > constexpr OutputIt reverse_copy( BidirIt first, BidirIt last, OutputIt d_first );			(since C++20)
template< class ExecutionPolicy, class BidirIt, class ForwardIt > ForwardIt reverse_copy( ExecutionPolicy&& policy, BidirIt first, BidirIt last, ForwardIt d_first );		(2)	(since C++17)

1) Copies the elements from the range [first, last) to another range beginning at d_first in such a way that the elements in the new range are in reverse order.

Behaves as if by executing the assignment *(d_first + (last - first) - 1 - i) = *(first + i) once for each non-negative i < (last - first)

If the source and destination ranges (that is, [first, last) and [d_first, d_first+(last-first)) respectively) overlap, the behavior is undefined.

2) Same as (1), but executed according to policy. This overload does not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true

Parameters

first, last	-	the range of elements to copy
d_first	-	the beginning of the destination range
Type requirements
- `BidirIt` must meet the requirements of LegacyBidirectionalIterator.
- `OutputIt` must meet the requirements of LegacyOutputIterator.
- `ForwardIt` must meet the requirements of LegacyForwardIterator.

Return value

Output iterator to the element past the last element copied.

Exceptions

The overload with a template parameter named ExecutionPolicy reports errors as follows:

If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation

See also the implementations in libstdc++ and libc++.

template<class BidirIt, class OutputIt>
OutputIt reverse_copy(BidirIt first, BidirIt last, OutputIt d_first)
{
    while (first != last) {
        *(d_first++) = *(--last);
    }
    return d_first;
}

Example

Run this code

#include <vector>
#include <iostream>
#include <algorithm>
 
int main()
{
    std::vector<int> v({1,2,3});
    for (const auto& value : v) {
        std::cout << value << " ";
    }
    std::cout << '\n';
 
    std::vector<int> destination(3);
    std::reverse_copy(std::begin(v), std::end(v), std::begin(destination));
    for (const auto& value : destination) {
        std::cout << value << " ";
    }
    std::cout << '\n';
}

Output:

1 2 3 
3 2 1

Complexity

Linear in the distance between first and last

Language
Standard Library Headers
Freestanding and hosted implementations
Named requirements
Language support library
Concepts library (C++20)
Diagnostics library
Utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications