有两个矩阵a和b，均为2行3列。求两个矩阵之和。重载运算符“+”，使之能用于矩阵相加（如c=a+b)

矩阵a和b的和为c，可以使用如下的重载运算符“+”：

#include <iostream>
#include <vector>

using namespace std;

class Matrix {
public:
    Matrix() {}

    Matrix(int r, int c) {
        resize(r, c);
    }

    void resize(int r, int c) {
        data.resize(r);
        for (int i = 0; i < r; ++i) {
            data[i].resize(c);
        }
    }

    friend Matrix operator+(const Matrix &a, const Matrix &b) {
        Matrix c(a.row(), a.col());
        for (int i = 0; i < a.row(); ++i) {
            for (int j = 0; j < a.col(); ++j) {
                c.data[i][j] = a.data[i][j] + b.data[i][j];
            }
        }
        return c;
    }

    int row() const {
        return data.size();
    }

    int col() const {
        return data[0].size();
    }

    int &operator()(int row, int col) {
        return data[row][col];
    }

    friend istream &operator>>(istream &in, Matrix &a) {
        for (int i = 0; i < a.row(); ++i) {
            for (int j = 0; j < a.col(); ++j) {
                in >> a(i, j);
            }
        }
        return in;
    }

    friend ostream &operator<<(ostream &out, const Matrix &a) {
        for (int i = 0; i < a.row(); ++i) {
            for (int j = 0; j < a.col(); ++j) {
                out << a(i, j) << ' ';
            }
            out << endl;
        }
        return out;
    }

private:
    vector<vector<int>> data;
};

int main() {
    Matrix a(2, 3), b(2, 3);
    cin >> a >> b;
    Matrix c = a + b;
    cout << c << endl;
    return 0;
}