Remember our code from Swapping, reversing, and partitioning to reverse the order of words in a sentence? When the "sentence" contains only two words, there is another way to look at the reversal: you could consider it a cyclic rotation of the elements in the underlying range. std::rotate(a,mid,b) rotates the elements of the range [a,b) so that the element formerly addressed by mid is now at a (and returns an iterator pointing to the element whose value was formerly at a):
template<class FwdIt>
FwdIt rotate(FwdIt a, FwdIt mid, FwdIt b)
{
auto result = a + (b - mid);
// First, reverse the whole range.
std::reverse(a, b);
// Next, un-reverse each individual segment.
std::reverse(a, result);
std::reverse(result, b);
return result;
}
void test()
{
std::vector<int> v = {1, 2, 3...
