Question

I am trying to rotate a vector of elements in C++. What I mean by that is that I have a vector<point> I want the last element to become the first.

Example:

[1,2,3] become [3,1,2] then [2,3,1]

For that I tried to do the following:

//Add the last element at index 0
ObjectToRotate.insert(0, ObjectToRotate.at(ObjectToRotate.size()-1));
//Remove Last element
ObjectToRotate.erase(ObjectToRotate.size()-1);

but I get this error:

Error 6 error C2664: ‘std::_Vector_iterator<_Myvec> std::vector<Ty>::insert<cv::Point<_Tp>&>(std::_Vector_const_iterator<_Myvec>,_Valty)’ : cannot convert parameter 1 from ‘int’ to ‘std::_Vector_const_iterator<_Myvec>’

How can I solve it?

Answer 1

There’s a std::rotate algorithm in the standard library:

std::rotate(ObjectToRotate.begin(),
            ObjectToRotate.end()-1, // this will be the new first element
            ObjectToRotate.end());