#include <iomanip>
#include <iostream>
#include <cstdlib>  // for rand()
using namespace std;

class Matrix
{
private:
    int** element;
    int rows;
    int cols;
    void alloc();
    void release();
public:
    Matrix(int = 0, int = 0);  // also default constructor
    Matrix(const Matrix&); // copy constructor
    ~Matrix();
    Matrix operator+(const Matrix&) const;
    Matrix& operator=(const Matrix&);
    friend ostream& operator<<(ostream&, const Matrix&);
};

int main()
{
    Matrix A(3,4), B(3,4), C;
    cout << A << endl;
    cout << B << endl;
    cout << C << endl;
    C = A + B;
    cout << C << endl;
}

Matrix::Matrix(int r, int c) : rows(r), cols(c)
{
    cout << "Constructor called for object " << this <<endl;
    alloc();

    // initialize Matrix elements with random numbers 0-9
    for (int i = 0; i < rows; i++)
        for (int j = 0; j < cols; j++)
            element[i][j] = rand()%10;
}

Matrix::Matrix(const Matrix& arg) : rows(arg.rows), cols(arg.cols)
{
    cout << "\nIn copy constructor for object " << this;
    cout << ", argument: " << &arg << endl;

    alloc();
    for (int i = 0; i < rows; i++)
        for (int j = 0; j < cols; j++)
            element[i][j] = arg.element[i][j];
}

Matrix::~Matrix()
{
    cout << "\n~~ Destructor called for object: " << this << endl;

    release();
}

void Matrix::alloc()        // allocate heap memory for elements
{
    cout << "Allocate memory for Matrix " << this << " elements\n";

    element = new int*[rows];
    for (int i = 0; i < rows; i++)
        element[i] = new int[cols];
}

void Matrix::release()
{
    cout << "I got rid of Matrix " << this << "'s elements\n";

    for (int i = 0; i < rows; i++)
        delete [] element[i];
    delete [] element;
}

Matrix Matrix::operator+(const Matrix& arg) const
{
    cout << "\nExecuting operator+ for object: " << this;
    cout << ", argument: " << &arg << endl;

    if (rows != arg.rows || cols != arg.cols)
    {
        cerr << "Invalid Matrix addition\n";
        return (*this);
    }

    Matrix temp(rows,cols);

    for (int i = 0; i < rows; i++)
        for (int j = 0; j < cols; j++)
            temp.element[i][j] = element[i][j] + arg.element[i][j];
    cout << temp << endl;
    return temp;
}

Matrix& Matrix::operator=(const Matrix& arg)
{
    cout << "\nExecuting operator= for object: " << this;
    cout << ", argument: " << &arg << endl;

    // Make sure rows and cols match the argument
    if (rows != arg.rows || cols != arg.cols)
    {
        release();
        rows = arg.rows;
        cols = arg.cols;
        alloc();
    }

    for (int i = 0; i < arg.rows; i++)
        for (int j = 0; j < arg.cols; j++)
            element[i][j] = arg.element[i][j];

    return *this;
}

ostream& operator<<(ostream& out, const Matrix& m)
{
    out << "\nMatrix values for object: "<< &m << endl;

    out << "----------------\n";

    for (int i = 0; i < m.rows; i++)
    {
        for (int j = 0; j < m.cols; j++)
            out << setw(4) << m.element[i][j];
        out << endl;
    }
    out << "----------------";
    return out;
}