std::rotate_copy

Copies the left rotation of [first, last) to d_first.

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

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

[edit] Parameters

[edit] Return value

Output iterator to the element past the last element copied.

[edit] Complexity

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

[edit] 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.

[edit] 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 middle,
 ForwardIt last, OutputIt d_first)
{
 d_first = std::copy (middle, last, d_first);
 return std::copy (first, middle, d_first);
}

[edit] 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

[edit] See also

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