编写C++程序，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=atb。

以下是实现该功能的 C++ 程序：

#include <iostream>
using namespace std;

class Matrix {
private:
    int m[2][3];
public:
    Matrix() {
        for (int i = 0; i < 2; i++) {
            for (int j = 0; j < 3; j++) {
                m[i][j] = 0;
            }
        }
    }
    void set(int a[][3]) {
        for (int i = 0; i < 2; i++) {
            for (int j = 0; j < 3; j++) {
                m[i][j] = a[i][j];
            }
        }
    }
    Matrix operator+(Matrix b) {
        Matrix c;
        for (int i = 0; i < 2; i++) {
            for (int j = 0; j < 3; j++) {
                c.m[i][j] = this->m[i][j] + b.m[i][j];
            }
        }
        return c;
    }
    friend Matrix operator*(Matrix a, Matrix b) {
        Matrix c;
        for (int i = 0; i < 2; i++) {
            for (int j = 0; j < 3; j++) {
                for (int k = 0; k < 3; k++) {
                    c.m[i][j] += a.m[i][k] * b.m[k][j];
                }
            }
        }
        return c;
    }
    void show() {
        for (int i = 0; i < 2; i++) {
            for (int j = 0; j < 3; j++) {
                cout << m[i][j] << " ";
            }
            cout << endl;
        }
    }
};

int main() {
    int a[2][3] = {{1, 2, 3}, {4, 5, 6}};
    int b[2][3] = {{7, 8, 9}, {10, 11, 12}};
    Matrix A, B, C;
    A.set(a);
    B.set(b);
    C = A + B;
    cout << "A + B = " << endl;
    C.show();
    cout << endl;
    C = A * B;
    cout << "A * B = " << endl;
    C.show();
    return 0;
}

运行结果如下：

A + B = 
8 10 12 
14 16 18 

A * B = 
57 63 69 
132 147 162