std::reverse_copy (3) - Linux Manuals

std::reverse_copy: std::reverse_copy

NAME

std::reverse_copy - std::reverse_copy

Synopsis

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

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