C/C++ :: Array Implementation Of Stack To Reverse Columns In Matrix

I had the following question in my exam paper and only got 1.5 out of a possible 6 marks. This is the question:

Given the Matrix class:

class Matrix {
public:
Matrix(unsigned r, unsigned c);
Matrix(const Matrix<T>& rhs);
~Matrix();
const Matrix<T>&operator=(const Matrix<T>& rhs);
[Code] ....

Use the linkedStackType class (Array implementation of stack) and write a function reverseCols to reverse the order of columns in the matrix. Note that reverseCols is not a member function of the Matrix class therefore only the public interface of matrix can be used.

//Implementation of Stacks as Array
template<class Type>
class stackType: public stackADT<Type> {
public:
const stackType<Type>& operator=(const stackType<Type>&);

[Code] ....

What is the correct solution must be to reverse the columns of the matrix?