题解 | #矩阵乘法#

#include <iostream>
#include <vector>
using namespace std;

//矩阵乘法
class MatrixMulti {
  private:
    //A是个x行y列的矩阵，B是个y行z列的矩阵
    int x, y, z;
    vector<vector<int>> A, B;

  public:
    //构造函数
    MatrixMulti(const int x, const int y, const int z);

    //析构函数
    ~MatrixMulti();

    //矩阵A,B相乘
    vector<vector<int>> multi(void)const;

    //<<重载（友元函数）
    friend ostream& operator<<(ostream& cout, vector<vector<int>>C);
};

MatrixMulti::MatrixMulti(const int x, const int y, const int z) {
    this->A.clear();
    this->B.clear();
    this->x = x;
    this->y = y;
    this->z = z;
    vector<int>vi;
    int a;
    for (int i = 0; i < x; i++) {
        vi.clear();
        for (int j = 0; j < y; j++) {
            cin >> a;
            vi.push_back(a);
        }
        this->A.push_back(vi);
    }
    for (int i = 0; i < y; i++) {
        vi.clear();
        for (int j = 0; j < z; j++) {
            cin >> a;
            vi.push_back(a);
        }
        this->B.push_back(vi);
    }
    return;
}

MatrixMulti::~MatrixMulti() {
}

vector<vector<int>> MatrixMulti::multi(void) const {
    vector<vector<int>>C;
    vector<int>vi;
    int a;
    for (int i = 0; i < x; i++) {
        vi.clear();
        for (int j = 0; j < z; j++) {
            a = 0;

            //计算a的值
            for (int k = 0; k < y; k++)
                a += this->A[i][k] * this->B[k][j];

            vi.push_back(a);
        }
        C.push_back(vi);
    }
    return C;
}

ostream& operator<<(ostream& cout, vector<vector<int>> C) {
    for (int i = 0; i < C.size(); i++) {
        cout << C[i][0];
        for (int j = 1; j < C[1].size(); j++)
            cout << ' ' << C[i][j];
        cout << endl;
    }
    // TODO: 在此处插入 return 语句
    return cout;
}

int main() {
    int a, b, c;
    while (cin >> a >> b >> c) { // 注意 while 处理多个 case
        cout << MatrixMulti(a, b, c).multi() << endl;
    }
}
// 64 位输出请用 printf("%lld")