C++中Matrix(矩阵)的基本运算( +、-、=、<<)

利用二维指针开辟空间形成二维数组；

原题为设计一个Matrix类，实现基本的矩阵运算；

初次设计为HL[10][10]数组，存放矩阵元素，后改为二维指针；

主要问题存在于二维指针理解的不透彻，无法理解其开辟空间的方法；

HL = new double *[row];
for(i = 0;i < row;i++)
    HL[i] = new double [list];

其次对于不同类型矩阵相加没有找到合适的处理方式，只能手动控制不使不同类型矩阵相加或相减；
其中 row 为行，list为列，HL为存放矩阵的二维指针；

附上一个new运算符的用法；

https://www.cnblogs.com/2015-16/p/11782595.html

#include<iostream>
using namespace std;

class Matrix
{
    private:
        int row,list;
        double **HL;
    public:
        Matrix(int r_ = 0, int l_ = 0);
        Matrix(int r_ , int l_ , double **newone);
        Matrix(const Matrix & rhs);
        ~Matrix();
        Matrix operator + (const Matrix & rhs);
        Matrix operator - (const Matrix & rhs);
        Matrix operator = (const Matrix & rhs);
        friend ostream & operator << (ostream & os , const Matrix & rhs);
};

int i,j;

Matrix::Matrix(int r_ , int l_):row(r_),list(l_)　　//构造函数
{
    HL = new double *[row];
    for(i = 0;i < row;i++)
        HL[i] = new double [list]; 
    cout<<"please enter Matrix :"<<endl;
    for(i = 0;i < row;i++)
        for(j = 0;j < list;j++)
            cin>>HL[i][j];
} 

Matrix::Matrix(int r_ , int l_ , double **newone ):row(r_),list(l_)　　//构造函数重载，主要用于加法减法中的return使用
{
    HL = new double *[row];
    for(i = 0;i < row;i++)
        HL[i] = new double [list]; 
    for(i = 0;i < row;i++)
        for(j = 0;j < list;j++)
            HL[i][j] = newone[i][j];
} 

Matrix::Matrix(const Matrix & rhs)
{
    if(this != & rhs)
    {
        this->row = rhs.row;
        this->list = rhs.list;
        HL = new double *[row];
        for(i = 0;i < row;i++)
            HL[i] = new double [list]; 
        for(i = 0;i < row;i++)
            for(j = 0;j < list;j++)
                this->HL[i][j] = rhs.HL[i][j];
    }
}

Matrix::~Matrix()　　　　//　析构函数，删除开辟的空间
{
    cout<<"~ Matrix : row ="<<row<<" , list = "<<list<<endl<<endl;
    for(i = 0;i < row;i++)
        delete [] HL[i];
    delete [] HL;
}

Matrix Matrix::operator + (const Matrix & rhs)
{
    if( (this->row == rhs.row)&&(this->list == rhs.list) )
    {
        double **newone;
        int r_,l_;
        r_ = row;l_ = list;
        newone = new double *[row];
        for(i = 0;i < row;i++)
            newone[i] = new double [list]; 
        for(i = 0;i < row;i++)
            for(j = 0;j < list;j++)
                newone[i][j] = HL[i][j] + rhs.HL[i][j];
        return Matrix(r_,l_,newone);
    }
//    else
//        cout<<"error ——矩阵类型不符 "<<endl; 
}

Matrix Matrix::operator - (const Matrix & rhs)
{
    if( (this->row == rhs.row)&&(this->list == rhs.list) )
    {
        double **newone;
        int r_,l_;
        r_ = row;l_ = list;
        newone = new double *[row];
        for(i = 0;i < row;i++)
            newone[i] = new double [list]; 
        for(i = 0;i < row;i++)
            for(j = 0;j < list;j++)
                newone[i][j] = HL[i][j] - rhs.HL[i][j];
        return Matrix(r_,l_,newone);
    }
//    else
//        cout<<"error ——矩阵类型不符 "<<endl; 
}

Matrix Matrix::operator = (const Matrix & rhs)
{
    if((this->row == rhs.row)&&(this->list == rhs.list))
    {
        for(i = 0;i < row;i++)
            for(j = 0;j < list;j++)
                this->HL[i][j] = rhs.HL[i][j];
        return (*this); 
    } 
//    else
//        cout<<"error ——矩阵类型不符 "<<endl; 
}

ostream & operator << (ostream & os,const Matrix & rhs)
{
    os<<"Matrix : row ="<<rhs.row<<" , list = "<<rhs.list<<endl;
    for(i = 0;i < rhs.row;i++)
    {
        for(j = 0;j < rhs.list;j++)
            os<<rhs.HL[i][j]<<" ";
        os<<endl;    
    }
    return os;
}

int main()
{
    int m,n,x,y;
    cin>>n>>m>>x>>y;
    Matrix aa(n,m),bb(n,m),cc(n,m),dd(x,y);
    cout<<endl<<aa<<endl<<bb<<endl<<cc<<endl<<dd<<endl;
    cout<<(aa+bb+cc)<<endl<<(cc-bb)<<endl;
    return 0;
} 

 2019-11-02    15:34:51