关于#c++#的问题：计算二维数组相加

哪位能帮我解释一下这个代码哪里出错了！

//重载+，<<,>>运算符，计算二维数组相加。
#include<iostream>
using namespace std;
class Mat
{
public:
    friend Mat operator+(Mat& a, Mat& b);
    friend istream operator>>(istream& in, Mat& a);
    friend ostream operator<<(ostream& cout, Mat& a);
    Mat();
    
private:
    int mat[2][3];
};
Mat::Mat()
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
            mat[i][j] = 0;
}

istream operator>>(istream& in, Mat& m)
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            cin >> m.mat[i][j];
        };
    return cin;
}
ostream operator<<(ostream& cout, Mat& m)
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            cout << m.mat[i][j];
        };
    return cout;
}
Mat operator+(Mat& a, Mat& b)
{
    Mat n;
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            n.mat[i][j] = a.mat[i][j] + b.mat[i][j];
        }
    return n;
}
int main()
{
    Mat a, b, c;
    cin >> a;
    cin >> b;
    cout << "a=" << a;
    cout << "b=" << b;
    c = a + b;
    cout << "c=" << c;
    
    system("pause");
    return 0;
}

在重载输入输出运算符时，应该使用流对象的引用，而不是对象本身。因此，在重载输入和输出运算符时，应该将参数的类型改为istream&和ostream&，并在返回值处返回相应的流对象。
此外，在输出运算符中，应该以空格或换行符分隔每个数字，而不是将它们挤在一起输出。
下面是修改后的代码：

#include<iostream>
using namespace std;

class Mat
{
public:
    friend Mat operator+(Mat& a, Mat& b);
    friend istream& operator>>(istream& in, Mat& a);
    friend ostream& operator<<(ostream& cout, Mat& a);

    Mat();
private:
    int mat[2][3];
};

Mat::Mat()
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
            mat[i][j] = 0;
}

istream& operator>>(istream& in, Mat& m)
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            in >> m.mat[i][j];
        };
    return in;
}

ostream& operator<<(ostream& cout, Mat& m)
{
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 3; j++) {
            cout << m.mat[i][j] << " ";
        }
        cout << endl;
    }
    return cout;
}

Mat operator+(Mat& a, Mat& b)
{
    Mat n;
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            n.mat[i][j] = a.mat[i][j] + b.mat[i][j];
        }
    return n;
}

int main()
{
    Mat a, b, c;
    cin >> a >> b;
    cout << "a=" << endl << a;
    cout << "b=" << endl << b;
    c = a + b;
    cout << "c=" << endl << c;

    system("pause");
    return 0;
}

修改如下：

//重载+，<<,>>运算符，计算二维数组相加。
#include<iostream>
using namespace std;
class Mat
{
public:
    friend Mat operator+(Mat& a, Mat& b);
    friend istream& operator>>(istream& in, Mat& a); // 返回加个 &
    friend ostream& operator<<(ostream& cout, Mat& a); // 返回加个 &
    Mat();
    
private:
    int mat[2][3];
};
Mat::Mat()
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
            mat[i][j] = 0;
}
 
istream& operator>>(istream& in, Mat& m) // 返回加个 &
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            cin >> m.mat[i][j];
        };
    return cin;
}
ostream& operator<<(ostream& cout, Mat& m) // 返回加个 &
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            cout << m.mat[i][j];
        };
    return cout;
}
Mat operator+(Mat& a, Mat& b)
{
    Mat n;
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            n.mat[i][j] = a.mat[i][j] + b.mat[i][j];
        }
    return n;
}
int main()
{
    Mat a, b, c;
    cin >> a;
    cin >> b;
    cout << "a=" << a <<endl; 
    cout << "b=" << b <<endl;
    c = a + b;
    cout << "c=" << c <<endl;
    
    system("pause");
    return 0;
}

这个代码有几个问题：

1.在类的定义中，重载输入输出运算符时应该使用friend istream& operator>>(istream& in, Mat& a)和friend ostream& operator<<(ostream& cout, Mat& a)，并且在函数定义中也应该加上返回值类型。

2.在重载输出运算符时，应该在输出每个元素后加上空格或换行，否则输出的结果会挤在一起。

修改后的代码如下：

#include<iostream>
using namespace std;
class Mat
{
public:
    friend Mat operator+(Mat& a, Mat& b);
    friend istream& operator>>(istream& in, Mat& a);
    friend ostream& operator<<(ostream& cout, Mat& a);
    Mat();
    
private:
    int mat[2][3];
};
Mat::Mat()
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
            mat[i][j] = 0;
}
 
istream& operator>>(istream& in, Mat& m)
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            in >> m.mat[i][j];
        };
    return in;
}
ostream& operator<<(ostream& cout, Mat& m)
{
    for (int i = 0; i < 2; i++)
    {
        for (int j = 0; j < 3; j++)
        {
            cout << m.mat[i][j] << " ";
        }
        cout << endl;
    }
    return cout;
}
Mat operator+(Mat& a, Mat& b)
{
    Mat n;
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            n.mat[i][j] = a.mat[i][j] + b.mat[i][j];
        }
    return n;
}
int main()
{
    Mat a, b, c;
    cin >> a;
    cin >> b;
    cout << "a=" << endl << a;
    cout << "b=" << endl << b;
    c = a + b;
    cout << "c=" << endl << c;
    
    system("pause");
    return 0;
}

在istream和ostream的函数声明中，返回类型应为istream&和ostream&，而不是istream和ostream:

istream& operator>>(istream& in, Mat& m)
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            cin >> m.mat[i][j];
        };
    return cin;
}

ostream& operator<<(ostream& cout, Mat& m)
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            cout << m.mat[i][j];
        };
    return cout;
}

• 你可以参考下这个问题的回答, 看看是否对你有帮助, 链接: https://ask.csdn.net/questions/7625539
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• 除此之外, 这篇博客: C++实现《数据结构与算法》相关算法--线性表中的 删除顺序表中指定位置i的数据元素 部分也许能够解决你的问题, 你可以仔细阅读以下内容或跳转源博客中阅读:
  

• // 表删除
  Status ListDelete_Sq(SqList& L, int i,ElemType &e) {
  	if ((i < 1) || (i > L.length))return ERROR; //判断i值不合法
  	e = L.elem[i - 1];
  	for (int j = i; j <= L.length - 1; j++)
  		L.elem[j - 1] = L.elem[j];             //被删除元素之后的元素向前迁移
  	L.length--;                                //表长减1
  	return OK;
  }
  

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