第十五周 项目2 用文件保存及格并且总分高于平均分学生名单

#include <iostream>
#include <fstream>
#include <cstdlib>
#include <string>
using namespace std;
//定义学生类
class Student
{
public:
Student() {};
~Student();
double get_total();
static int get_stu_num();
static double get_total_sum();
friend istream& operator>>(istream &in, Student &s);
friend ostream& operator<<(ostream &out, Student &s);
bool pass();
private:
string name;
double cpp;
double math;
double english;
double total;
static int stu_num;  //学生人数，处理为类的静态成员合适
static double total_sum; //学生总分和
};

int Student::stu_num = 0;
double Student::total_sum = 0;
Student::~Student()
{
total_sum-=total;
stu_num--;
}

double Student::get_total()
{
return total;
}

int Student::get_stu_num()
{
return stu_num;
}

double Student::get_total_sum()
{
return total_sum;
}

istream& operator>>(istream &in, Student &s)
{
in>>s.name>>s.cpp>>s.math>>s.english;
s.total=s.cpp+s.math+s.english;
Student::stu_num++;   //在读入数据过程中，用静态成员记录下来具体的学生人数和总分和
Student::total_sum+=s.total;
return in;
}

ostream &operator<<(ostream &out, Student &s)
{
out<<s.name<<"\t";
out<<s.cpp<<"\t";
out<<s.math<<"\t";
out<<s.english<<"\t";
out<<s.total;
return out;
}

//返回是否所有课程全过了
bool Student::pass()
{
return cpp>=60 && math>=60 && english>=60;
}

int main( )
{
Student stud[200],t; //stud[200]为保存数据的对象数组
string sname;
double total_avg;
int i=0;
//从文件score.dat中读入数据，保存到对象数组中
ifstream infile("score.dat",ios::in);
if(!infile)
{
cerr<<"open error"<<endl;
exit(1);
}
//for(i=0;i<Student::get_stu_num;i++)
while(!infile.eof())
{
infile>>stud[i++];
}
infile.close();

//总分高于平均总分且没挂科的同学的信息保存到文件pass_score.dat中
ofstream outfile("pass_score.txt",ios::out);
if(!outfile)
{
cerr<<"open error"<<endl;
exit(1);
}
if(Student::get_stu_num()>0)
{
total_avg=Student::get_total_sum()/Student::get_stu_num();
for(i=0;i<Student::get_stu_num();i++)
{
if(stud[i].get_total()>total_avg&&stud[i].pass())
{
outfile<<stud[i]<<endl;
}
}
}
outfile.close();

return 0;
}