C++中實現矩陣的加法和乘法實例

#include<iostream>
using namespace std;

class Matrix
{
  int row;//矩陣的行
  int col;//矩陣的列
  int **a;//保存二維數組的元素
public:
  Matrix();//默認構造函數
  Matrix(int r, int c);
  Matrix(const Matrix &is);//拷貝構造函數
  void Madd(const Matrix &is);//矩陣加
  Matrix Mmul(const Matrix &is);//矩陣乘
  void display();//顯示矩陣元素
};

Matrix::Matrix(int r, int c)
{
  row = r;
  col = c;
  a = (int **)malloc(sizeof(int*)*row);
  for (int r = 0; r < row; r++)
  {
    *(a + r) = (int*)malloc(sizeof(int)*col);
  }
  printf("請輸入數：\n");
  for (int i = 0; i < row; i++)
    for (int j = 0; j < col; j++)
      cin >> a[i][j];
}

Matrix::Matrix(const Matrix & is)
{//拷貝構造函數
  row = is.row;
  col = is.col;
  a = new int*[row];
  for (int i = 0; i < row; i++)
  {
    a[i] = new int[col];
  }
  a = is.a;
}

void Matrix::Madd(const Matrix & is)
{
  if (row != is.row || col != is.col)//判斷兩矩陣是否符合相加條件
  {
    cout << "相加的矩陣必須行和列一致";
  }
  else
  {
    for (int i = 0; i < row; i++)
    {
      for (int j = 0; j < col; j++)
      {
        a[i][j] += is.a[i][j];
      }
    }
  }
}

Matrix Matrix::Mmul(const Matrix & is)
{
  Matrix M3(this->row, is.col);
  if (this->col != is.row)//判斷是否符合相乘條件
  {
    cout << "不符合兩矩陣相乘的條件";
  }
  else
  {
    for (int i = 0; i < M3.row; i++)
    {
      for (int j = 0; j < M3.col; j++)
      {
        M3.a[i][j] = 0;
        for (int n = 0; n < is.row; n++)
        {
          M3.a[i][j] += this->a[i][n] * is.a[n][j];
        }
      }
    }
  }
  return M3;
}

void Matrix::display()
{//輸出矩陣
  for (int i = 0; i < row; i++)
  {
    for (int j = 0; j < col; j++)
    {
      cout << a[i][j] << " ";
    }
    cout << endl;
  }
  cout << endl;
}

int main()
{
  Matrix m1(3, 3);
  m1.display();
  Matrix m2(3, 3);
  m2.display();
  Matrix m3(3, 2);
  m3.display();
  cout << "m1+m2=" << endl;
  m1.Madd(m2);
  m1.display();
  Matrix m4(m1.Mmul(m3));
  cout << "m1*m3=" << endl;
  m4.display();
  system("pause");
  return 0;
}