Perform Matrix Addition in C++

#include <iostream>

void addMatrices(const int mat1[][3], const int mat2[][3], int result[][3], int rows, int cols) {
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            result[i][j] = mat1[i][j] + mat2[i][j];
        }
    }
}

void displayMatrix(const char* title, const int matrix[][3], int rows, int cols) {
    std::cout << title << "\n";
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            std::cout << matrix[i][j] << " ";
        }
        std::cout << "\n";
    }
}

int main() {
    int matrix1[3][3] = {
        { 1, 2, 3 },
        { 4, 5, 6 },
        { 7, 8, 9 },
    };
    int matrix2[3][3] = {
        { 9, 8, 7 },
        { 6, 5, 4 },
        { 3, 2, 1 },
    };
    int resultMatrix[3][3];

    addMatrices(matrix1, matrix2, resultMatrix, 3, 3);

    displayMatrix("Matrix 1:", matrix1, 3, 3);
    std::cout << "\n";
    displayMatrix("Matrix 2:", matrix2, 3, 3);
    std::cout << "\n";
    displayMatrix("Resultant Matrix:", resultMatrix, 3, 3);
    return 0;
}

#include <iostream>

void addMatrices2x2(const int a[][2], const int b[][2], int result[][2]) {
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2; j++) {
            result[i][j] = a[i][j] + b[i][j];
        }
    }
}

void printMatrix(const char* title, const int m[][2]) {
    std::cout << title << "\n";
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2; j++) {
            std::cout << m[i][j] << " ";
        }
        std::cout << "\n";
    }
}

int main() {
    int a[2][2] = {
        { 1, 2 },
        { 3, 4 },
    };
    int b[2][2] = {
        { 4, 3 },
        { 2, 1 },
    };
    int c[2][2];
    addMatrices2x2(a, b, c);

    printMatrix("A", a);
    std::cout << "\n";
    printMatrix("B", b);
    std::cout << "\n";
    printMatrix("A + B", c);
    return 0;
}

#include <iostream>
#include <string>
#include <vector>

using Matrix = std::vector<std::vector<int>>;

bool sameShape(const Matrix& a, const Matrix& b) {
    if (a.empty() || b.empty() || a.size() != b.size()) {
        return false;
    }
    if (a[0].empty() || a[0].size() != b[0].size()) {
        return false;
    }
    for (size_t i = 0; i < a.size(); i++) {
        if (a[i].size() != a[0].size() || b[i].size() != a[0].size()) {
            return false;
        }
    }
    return true;
}

bool addMatricesSafe(const Matrix& a, const Matrix& b, Matrix& result) {
    if (!sameShape(a, b)) {
        return false;
    }
    size_t rows = a.size();
    size_t cols = a[0].size();
    result.assign(rows, std::vector<int>(cols));
    for (size_t i = 0; i < rows; i++) {
        for (size_t j = 0; j < cols; j++) {
            result[i][j] = a[i][j] + b[i][j];
        }
    }
    return true;
}

std::string matrixToString(const Matrix* m) {
    if (m == nullptr) {
        return "null";
    }
    std::string s = "[";
    for (size_t i = 0; i < m->size(); i++) {
        if (i > 0) s += ", ";
        s += "[";
        for (size_t j = 0; j < (*m)[i].size(); j++) {
            if (j > 0) s += ", ";
            s += std::to_string((*m)[i][j]);
        }
        s += "]";
    }
    s += "]";
    return s;
}

int main() {
    Matrix okInA = { { 1, 2 }, { 3, 4 } };
    Matrix okInB = { { 4, 3 }, { 2, 1 } };
    Matrix badInA = { { 1, 2 } };
    Matrix badInB = { { 1, 2 }, { 3, 4 } };

    Matrix ok;
    Matrix* okPtr = addMatricesSafe(okInA, okInB, ok) ? &ok : nullptr;
    Matrix bad;
    Matrix* badPtr = addMatricesSafe(badInA, badInB, bad) ? &bad : nullptr;

    std::cout << matrixToString(okPtr) << "\n";
    std::cout << matrixToString(badPtr) << "\n";
    return 0;
}