14.2用文件保存学生名单

#include <iostream>
#include<fstream>
#include<cstdlib>
#include<cstring>
using namespace std;
class student
{
public:
    string name;
    double cpp;
    double math;
    double english;
    double total;
    static int stu_num;
    static double total_sum;
    void sum();
    bool pass(double);
};
int student::stu_num=0;
double student::total_sum=0;
void student::sum()
{
    total=cpp+math+english;
}
bool student::pass(double avg)
{
    if(total>avg && cpp>60 && math>60 && english>60)
       return true;
    else
        return false;
}
int main()
{
    student stud[200],t;
    string sname;
    double total_avg;
    int i=0;
    ifstream infile("score.dat",ios::in);
    if(!infile)
    {
        cerr<<"not infile"<<endl;
        exit(1);
    }
    while(!infile.eof())
    {
        infile>>stud[i].name>>stud[i].cpp>>stud[i].math>>stud[i].english;
        stud[i].sum();
        ++i;
    }
    infile.close();
    student::stu_num=i;
    while(i)
    {
        i--;
        student::total_sum+=stud[i].total;
    }
    total_avg=(student::total_sum)/(student::stu_num);
    ofstream outfile("pass_score.dat",ios::out);
     if(!outfile)
     {
         cerr<<"open error"<<endl;
         exit(1);
     }
     while(student::stu_num>i)
     {
         if(stud[i].pass(total_avg))
         {
             outfile<<stud[i].name<<stud[i].cpp<<stud[i].math<<stud[i].english;
         }
         i++;
     }
     outfile.close();
    return 0;
}