#include<iostream> using namespace std; class Complex { private: double real; double imag; public: Complex(double r=0.0,double i=0.0) { real = r; imag = i; } friend Complex operator + (Complex c1, Complex c2); friend Complex operator - (Complex c1, Complex c2); void display(); }; Complex Complex:: operator +(Complex c1, Complex c2) { Complex c; c.real = c1.real + c2.real; c.imag = c1.imag + c2.imag; return c; } Complex Complex:: operator -(Complex c1, Complex c2) { Complex c; c.real = c1.real - c2.real; c.imag = c1.imag - c2.imag; return c; } void Complex::display() { cout << "(" << real << "," << imag << ")" << endl; } int main() { Complex c1(4, 3), c2(2, 1), c3; cout << "c1="; c1.display(); cout << "c2="; c2.display(); c3 = c1 - c2; cout << "c3="; c3.display(); c3 = c1 + c2; cout << "c3="; c3.display(); return 0; } 存在的问题

代码中存在以下问题：

1. 缺少头文件：需要添加头文件 `#include<iostream>`。

2. 命名空间使用不规范：应该避免在头文件中使用 `using namespace std;`，而是应该在使用标准库的时候显式地使用 `std::`。

3. 运算符重载函数的定义方式不正确：应该将运算符重载函数定义为类的成员函数，或者定义为友元函数。在代码中，运算符重载函数应该写成 `Complex Complex::operator+(Complex c2)` 和 `Complex Complex::operator-(Complex c2)`。

4. 运算符重载函数的参数传递方式不正确：在运算符重载函数中，需要将当前对象作为一个参数传入。在代码中，应该将运算符重载函数定义为友元函数，并且将两个对象作为参数传入，在函数中分别访问它们的私有成员变量。

5. 类方法的定义方式不规范：在定义类方法时，应该将方法的实现写在类定义的外面，而不是写在类定义内部。

6. 对象的初始化方式不规范：在定义对象时，应该避免使用默认构造函数的方式进行初始化，而是应该使用带参数的构造函数进行初始化。在代码中，应该将 `Complex c1(4, 3), c2(2, 1), c3;` 改为 `Complex c1(4, 3), c2(2, 1), c3(0, 0);`。

下面是修改后的代码：

#include<iostream>

class Complex {
private:
    double real;
    double imag;
public:
    Complex(double r=0.0, double i=0.0) {
        real = r;
        imag = i;
    }
    Complex operator+(Complex c2);
    Complex operator-(Complex c2);
    void display();
};

Complex Complex::operator+(Complex c2) {
    Complex c;
    c.real = real + c2.real;
    c.imag = imag + c2.imag;
    return c;
}

Complex Complex::operator-(Complex c2) {
    Complex c;
    c.real = real - c2.real;
    c.imag = imag - c2.imag;
    return c;
}

void Complex::display() {
    std::cout << "(" << real << "," << imag << ")" << std::endl;
}

int main() {
    Complex c1(4, 3), c2(2, 1), c3(0, 0);
    std::cout << "c1=";
    c1.display();
    std::cout << "c2=";
    c2.display();
    c3 = c1 - c2;
    std::cout << "c3=";
    c3.display();
    c3 = c1 + c2;
    std::cout << "c3=";
    c3.display();
    return 0;
}