Example: Matrix Addition using Class Example in C++

// Matrix Addition using Class Example
#include <iostream>
#include <vector> // Required for std::vector
using namespace std; // Using namespace std as per instructions

// Define the Matrix class
class Matrix {
private:
    int rows;
    int cols;
    vector<vector<int>> data; // Using std::vector for dynamic 2D array

public:
    // Constructor to initialize matrix dimensions and resize data vector
    Matrix(int r, int c) : rows(r), cols(c) {
        if (r <= 0 || c <= 0) {
            cerr << "Error: Matrix dimensions must be positive." << endl;
            this->rows = 0; // Indicate an invalid matrix
            this->cols = 0;
        } else {
            data.resize(rows, vector<int>(cols));
        }
    }

    // Method to get matrix elements from the user
    void input() {
        if (rows == 0 || cols == 0) {
            cerr << "Cannot input into an uninitialized or invalid matrix." << endl;
            return;
        }
        cout << "Enter elements for a " << rows << "x" << cols << " matrix:" << endl;
        for (int i = 0; i < rows; ++i) {
            for (int j = 0; j < cols; ++j) {
                cout << "Enter element at position [" << i + 1 << "][" << j + 1 << "]: ";
                cin >> data[i][j];
            }
        }
    }

    // Method to display the matrix elements
    void display() const {
        if (rows == 0 || cols == 0) {
            cout << "Matrix is empty or invalid." << endl;
            return;
        }
        for (int i = 0; i < rows; ++i) {
            for (int j = 0; j < cols; ++j) {
                cout << data[i][j] << "\t";
            }
            cout << endl;
        }
    }

    // Method to add two matrices
    Matrix add(const Matrix& other) const {
        // Check if dimensions are compatible for addition
        if (rows != other.rows || cols != other.cols) {
            cerr << "Error: Matrices must have the same dimensions for addition." << endl;
            return Matrix(0, 0); // Return an invalid matrix
        }

        // Create a new matrix to store the result of the addition
        Matrix result(rows, cols);
        for (int i = 0; i < rows; ++i) {
            for (int j = 0; j < cols; ++j) {
                result.data[i][j] = this->data[i][j] + other.data[i][j];
            }
        }
        return result;
    }

    // Getter methods for dimensions (useful for external checks)
    int getRows() const { return rows; }
    int getCols() const { return cols; }
};

int main() {
    // Step 1: Get dimensions for the first matrix from the user
    int r1, c1;
    cout << "Enter the number of rows for Matrix 1: ";
    cin >> r1;
    cout << "Enter the number of columns for Matrix 1: ";
    cin >> c1;

    // Step 2: Create Matrix 1 object and get its elements
    Matrix mat1(r1, c1);
    mat1.input();

    // Step 3: Get dimensions for the second matrix from the user
    int r2, c2;
    cout << "\nEnter the number of rows for Matrix 2: ";
    cin >> r2;
    cout << "Enter the number of columns for Matrix 2: ";
    cin >> c2;

    // Step 4: Create Matrix 2 object and get its elements
    Matrix mat2(r2, c2);
    mat2.input();

    // Step 5: Display Matrix 1
    cout << "\n--- Matrix 1 ---" << endl;
    mat1.display();

    // Step 6: Display Matrix 2
    cout << "\n--- Matrix 2 ---" << endl;
    mat2.display();

    // Step 7: Check if matrices can be added and perform addition
    if (mat1.getRows() == mat2.getRows() && mat1.getCols() == mat2.getCols()) {
        Matrix sumMat = mat1.add(mat2);
        cout << "\n--- Sum of Matrices ---" << endl;
        sumMat.display();
    } else {
        cout << "\nError: Cannot add matrices. Dimensions mismatch!" << endl;
    }

    return 0;
}