std:: rotate_copy

If any of the following conditions is satisfied, the behavior is undefined:

• [ first , n_first ) or [ n_first , last ) is not a valid range .
• The source and destination ranges overlap.

Parameters

Return value

Output iterator to the element past the last element copied.

Complexity

Exactly std:: distance ( first, last ) assignments.

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++ , libc++ , and MSVC STL .

template<class ForwardIt, class OutputIt>
constexpr // since C++20
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 <iostream>
#include <iterator>
#include <vector>
 
int main()
{
    std::vector<int> src{1, 2, 3, 4, 5};
    std::vector<int> dest(src.size());
    auto pivot = std::find(src.begin(), src.end(), 3);
 
    std::rotate_copy(src.begin(), pivot, src.end(), dest.begin());
    for (int i : dest)
        std::cout << i << ' ';
    std::cout << '\n';
 
    // copy the rotation result directly to the std::cout
    pivot = std::find(dest.begin(), dest.end(), 1);
    std::rotate_copy(dest.begin(), pivot, dest.end(),
                     std::ostream_iterator<int>(std::cout, " "));
    std::cout << '\n';
}

3 4 5 1 2
1 2 3 4 5

See also