C++中常见的代码重用问题详解

// 传值方式
void funcByValue(int num) {
    num += 10;
}

// 传引用方式
void funcByReference(int& num) {
    num += 10;
}

// 传指针方式
void funcByPointer(int* num) {
    *num += 10;
}

int main() {
    int num = 10;
    
    funcByValue(num);
    cout << "传值方式：" << num << endl;  // 输出：10
    
    funcByReference(num);
    cout << "传引用方式：" << num << endl;  // 输出：20
    
    funcByPointer(&num);
    cout << "传指针方式：" << num << endl;  // 输出：30
    
    return 0;
}

void print(int num) {
    cout << "打印整数：" << num << endl;
}

void print(double num) {
    cout << "打印浮点数：" << num << endl;
}

int main() {
    int num1 = 10;
    double num2 = 3.14;
    
    print(num1);  // 输出：打印整数：10
    print(num2);  // 输出：打印浮点数：3.14
    
    return 0;
}

class Shape {
public:
    virtual double area() = 0;
};

class Rectangle : public Shape {
private:
    double width;
    double height;
    
public:
    Rectangle(double w, double h) : width(w), height(h) {}
    
    double area() override {
        return width * height;
    }
};

class Square : public Rectangle {
public:
    Square(double side) : Rectangle(side, side) {}
};

int main() {
    Rectangle rect(4, 5);
    cout << "矩形面积：" << rect.area() << endl;  // 输出：矩形面积：20
    
    Square square(5);
    cout << "正方形面积：" << square.area() << endl;  // 输出：正方形面积：25
    
    return 0;
}

class Animal {
public:
    virtual void sound() {
        cout << "动物发出声音" << endl;
    }
};

class Cat : public Animal {
public:
    void sound() override {
        cout << "猫叫声：喵喵喵" << endl;
    }
};

class Dog : public Animal {
public:
    void sound() override {
        cout << "狗叫声：汪汪汪" << endl;
    }
};

int main() {
    Animal* animal1 = new Cat();
    Animal* animal2 = new Dog();
    
    animal1->sound();  // 输出：猫叫声：喵喵喵
    animal2->sound();  // 输出：狗叫声：汪汪汪
    
    delete animal1;
    delete animal2;
    
    return 0;
}

template<typename T>
class Base {
public:
    void print() {
        T obj;
        obj.sayHello();
    }
};

class Derived1 : public Base<Derived1> {
public:
    void sayHello() {
        cout << "派生类1打招呼" << endl;
    }
};

class Derived2 : public Base<Derived2> {
public:
    void sayHello() {
        cout << "派生类2打招呼" << endl;
    }
};

int main() {
    Derived1 d1;
    d1.print();  // 输出：派生类1打招呼
    
    Derived2 d2;
    d2.print();  // 输出：派生类2打招呼
    
    return 0;
}

template<typename T>
class Math {
public:
    static T add(T a, T b) {
        return a + b;
    }
};

template<>
class Math<string> {
public:
    static string add(string a, string b) {
        return a + b;
    }
};

int main() {
    int a = 10, b = 20;
    cout << "整数相加：" << Math<int>::add(a, b) << endl;  // 输出：整数相加：30
    
    double c = 3.14, d = 2.72;
    cout << "浮点数相加：" << Math<double>::add(c, d) << endl;  // 输出：浮点数相加：5.86
    
    string e = "Hello", f = "world!";
    cout << "字符串相加：" << Math<string>::add(e, f) << endl;  // 输出：字符串相加：Hello world!
    
    return 0;
}