Difference between revisions of "cpp/algorithm/reverse copy"

Revision as of 20:13, 14 August 2013

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 *(result + (last - first) - 1 - i) = *(first + i) once for each non-negative i < (last - first)

If the ranges [first, last) and [result, result+(last-first)) overlap, the behavior is undefined.

Parameters

Return value

Output iterator to the element past the last element copied.

Possible implementation

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

#include <vector>
#include <iostream>
#include <algorithm>
 
int main()
{
    std::vector<int> v({1,2,3});
    std::for_each(std::begin(v), std::end(v),
                  [&](int value){ std::cout << value << " "; });
    std::cout << std::endl;
 
    std::vector<int> destiny(3);
    std::reverse_copy(std::begin(v), std::end(v), std::begin(destiny));
    std::for_each(std::begin(destiny), std::end(destiny),
                  [&](int value){ std::cout << value << " "; });
    std::cout << std::endl;
}

1 2 3 
3 2 1

Complexity

linear in the distance between first and last

See also