// Matrix

#include <string>
#include <sstream>
#include <iostream>
#include <vector>
//#include <exception>

/////////////////////////////////////////////////////////////
// class Row
//   no copy ctor, dtor, or assignment operator needed

template <typename T>
class Row
{
public:
  Row(int i);
  T& operator[](int i);
  T operator[](int i) const;
private:
  int _NumRows;
  std::vector<T> _rowData;
};

template <typename T>
Row<T>::Row(int i) : _NumRows(i)
{
  for(int j=0; j<i; ++j)
    _rowData.push_back(0);
}

template <typename T>
T& Row<T>::operator[](int i)
{
  if(i<0 || _NumRows<=i)
    throw std::range_error("index out of bounds in Row[]");
  return _rowData[i];
}

template <typename T>
T Row<T>::operator[](int i) const
{
  if(i<0 || _NumRows<=i)
    throw std::range_error("index out of bounds in Row[]");
  return _rowData[i];
}

/////////////////////////////////////////////////////////////
// class Matrix
//   no copy ctor, dtor, or assignment operator are needed

template <typename T>
class Matrix
{
public:
  Matrix(int i, int j);
  Row<T>& operator[](int i);
  Row<T> operator[](int i) const;
  int rows();
  int cols();
  std::string show();
private:
  int _NumRows, _NumCols;
  std::vector< Row<T> > _matrixData;
};

template <typename T>
Matrix<T>::Matrix(int i, int j) : _NumRows(i), _NumCols(j)
{
  for(int k=0; k<i; ++k)
  {
    Row<T> temp(j);
    _matrixData.push_back(temp);
  }
}

template <typename T>
int Matrix<T>::rows() { return _NumRows; }

template <typename T>
int Matrix<T>::cols() { return _NumCols; }

template <typename T>
Row<T>& Matrix<T>::operator [](int i)
{
  if(i<0 || _NumRows<=i)
    throw std::range_error("index out of range in Matrix<T>::operator[]");
  return _matrixData[i];
}

template <typename T>
std::string Matrix<T>::show()
{
  std::ostringstream temp("");
  for(int i=0; i<rows(); ++i)
  {
    temp << "\n  ";
    for(int j=0; j<cols(); ++j)
      temp << (*this)[i][j] << " ";
  }
  temp << "\n";
  return temp.str();
}

int main()
{
  Matrix<int> m(3,4);
  for(int i=0; i<m.rows(); ++i)
    for(int j=0; j<m.cols(); ++j)
      m[i][j] = i+j;

  std::cout << m.show() << "\n\n";

  Matrix<int> n = m;
  std::cout << n.show() << "\n\n";

  Matrix<int> p(2,5);
  p = m;
  std::cout << p.show() << "\n\n";
}