作业4.21

#include<iostream>#include<string>using namespace std;class student{public:student(string name1,string num1,int score1);void show();static void show_count_sum_ave();private:string name;int score;static int count;static float sum;static float ave;string num;};student::student(string name1,string num1,int score1){name=name1;score=score1;num=num1;++count;sum=sum+score;ave=sum/count;}void student::show(){cout<<"姓名:"<<name<<endl     <<"成绩:"<<score<<endl <<"学号:"<<num<<endl;}void student::show_count_sum_ave(){cout<<"学生人数:"<<count<<endl<<"学生总成绩:"<<sum<<endl<<"平均成绩:"<<ave<<endl;}int student::count=0;float student::ave=0.0;float student::sum=0.0;int main(){student stu1("xiaoming","111111",75);stu1.show();  student stu2("xiaohong","111112",76);  stu2.show();  stu2.show_count_sum_ave();  return 0;}