第四章第二十一题


#include<iostream>

#include<string>

using namespace std;

class student{

public:

 student(int id1,string name1,double score1);

 void show();

 static void show_count_sum_ave();

private:

 int id;

 string name;

 double score;

 static int count;

 static double sum;

 static double ave;

};

student::student(int id1,string name1,double score1)

{id=id1;

name=name1;

score=score1;

++count;

sum=sum+score;

ave=sum/count;

}

void student::show()

{cout<<"姓名:"<<name<<endl;

cout<<"学号:"<<id<<endl;

cout<<"成绩:"<<score<<endl;

}

void student::show_count_sum_ave()

{cout<<"学生人数:"<<count<<endl;

cout<<"学生总成绩:"<<sum<<endl;

cout<<"学生平均成绩:"<<ave<<endl;

}

int student::count=0;

double student::sum=0.0;

double student::ave=0.0;

int main()

{student stu1(01,"zhangsan",90);

stu1.show();

student::show_count_sum_ave();

student stu2(02,"lisi",80);

stu2.show();

student::show_count_sum_ave();

student stu3(03,"wangwu",70);

stu3.show();

student::show_count_sum_ave();

return 0;

}