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std::rotate_copy

Defined in header `<algorithm>`
	(1)
template< class ForwardIt, class OutputIt > OutputIt rotate_copy( ForwardIt first, ForwardIt n_first, ForwardIt last, OutputIt d_first );		(until C++20)
template< class ForwardIt, class OutputIt > constexpr OutputIt rotate_copy( ForwardIt first, ForwardIt n_first, ForwardIt last, OutputIt d_first );		(since C++20)
template< class ExecutionPolicy, class ForwardIt1, class ForwardIt2 > ForwardIt2 rotate_copy( ExecutionPolicy&& policy, ForwardIt1 first, ForwardIt1 n_first, ForwardIt1 last, ForwardIt2 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 element n_first becomes the first element of the new range and n_first - 1 becomes the last element.

2) Same as (1), but executed according to policy. This overload only participates in overload resolution if std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true

Parameters

first, last	-	the range of elements to copy
n_first	-	an iterator to an element in `[first, last)` that should appear at the beginning of the new range
d_first	-	beginning of the destination range
policy	-	the execution policy to use. See execution policy for details.
Type requirements
-`ForwardIt, ForwardIt1, ForwardIt2` must meet the requirements of ForwardIterator.
-`OutputIt` must meet the requirements of OutputIterator.

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 three 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

template<class ForwardIt, class OutputIt>
OutputIt rotate_copy(ForwardIt first, ForwardIt n_first,
                           ForwardIt last, OutputIt d_first)
{
    d_first = std::copy(n_first, last, d_first);
    return std::copy(first, n_first, d_first);
}

Example

#include <algorithm>
#include <vector>
#include <iostream>
 
int main()
{
    std::vector<int> src = {1, 2, 3, 4, 5}; 
    auto pivot = std::find(src.begin(), src.end(), 3); 
    std::vector<int> dest(src.size());                                          
 
    std::rotate_copy(src.begin(), pivot, src.end(), dest.begin());
 
    for (const auto &i : dest) {
        std::cout << i << ' ';
    }   
    std::cout << '\n';
}

Output:

3 4 5 1 2

Complexity

linear in the distance between first and last.