Appending a C-array to a vector in reverse order in C++98/03 without a for-loop

Question

Its pretty straightforward to append a C-array to a vector (in C++ 98/03) like so:

std::vector<int> vec;
const int array[5] = { 1 , 2 , 3 , 4 , 5};

vec.insert( vec.end() , array , array + 5 );

Is there a way to append the array to a vector in reverse order in C++98/03 without writing a for-loop. (Here's looking at you Sean Parent.)

Answer 1

There you go. Use std::reverse_copy with std::back_inserter to add elements to the vector:

std::vector<int> vec;
int array[5] = { 1 , 2 , 3 , 4 , 5};

std::reverse_copy(array , array + 5, std::back_inserter(vec));

If you're concerned about performance, don't forget to reserve() before copying.

Answer 2

vec.insert(std::end(vec),
           std::rbegin(array),
           std::rend(array));

Note that this uses C++14, but reverse iterators have been around much longer, you would just need to create them manually if stuck with an older standard:

int const a1[] = {1, 2, 3, 4, 5};
int a2[5];
std::copy(std::reverse_iterator<int const*>(std::end(a1)),
          std::reverse_iterator<int const*>(std::begin(a1)),
          std::begin(a2)); // copy in reverse

std::copy(std::begin(a2),
          std::end(a2),
          std::ostream_iterator<int>(std::cout, " ")); // prints "5 4 3 2 1 "