#include <iostream> #include<string> using namespace std; class Student {public: Student(int n, string nam ) {num=n; name=nam; } void display() {cout<<"num:"<<num<<endl; cout<<"name:"<<name<<endl; } protected: int num; string name; }; class Student1: public Student {public: 空缺 {age=a; } void show( ) {display(); cout<<"age: "<<age<<endl; } private: int age; }; class Student2:public Student1 {public: 空缺 {score=s;} void show_all() {show(); cout<<"score:"<<score<<endl; } private: int score; }; int main( ) {Student2 stud(10010,"Li",17,89); stud.show_all( ); 补全 return 0; }

在主函数中，需要补全一个输出语句，以便输出 stud 对象的信息。

可以在 stud.show_all() 函数调用之后，加上一行代码：

cout << "Student2 object information:" << endl;

这样就可以在输出学生的信息之前，先输出一条描述信息，以便更好地区分输出内容。完整的代码如下：

#include <iostream> 
#include <string> 

using namespace std; 

class Student { 
public: 
    Student(int n, string nam) { 
        num = n; name = nam; 
    } 
    void display() { 
        cout << "num:" << num << endl; 
        cout << "name:" << name << endl; 
    } 
protected: 
    int num; 
    string name; 
}; 

class Student1 : public Student { 
public: 
    Student1(int n, string nam, int a) : Student(n, nam) { 
        age = a; 
    } 
    void show() { 
        display(); 
        cout << "age: " << age << endl; 
    } 
private: 
    int age; 
}; 

class Student2 : public Student1 { 
public: 
    Student2(int n, string nam, int a, int s) : Student1(n, nam, a) { 
        score = s; 
    } 
    void show_all() { 
        show(); 
        cout << "score: " << score << endl; 
    } 
private: 
    int score; 
}; 

int main() { 
    Student2 stud(10010, "Li", 17, 89); 
    cout << "Student2 object information:" << endl;
    stud.show_all(); 
    return 0; 
}

执行程序后，输出结果如下：

Student2 object information:
num:10010
name:Li
age: 17
score: 89