*作者：王忠
*完成日期：2015.6.09

*版本號：v1.0
*
*問題描述：檔案score.dat中儲存的是若干名學生的姓名和C++課、高數和英語成績。
（1）定義學生類，其中包含姓名、C++課、高數和英語成績及總分資料成員。
（2）用物件陣列進行儲存學生的成績，讀入成績並計算總分；將總分高於平均總分且沒掛科的同學的資訊儲存到檔案pass_score.dat中。

*輸入描述：

*程式輸出：

#include <iostream>
#include <cstdlib>
#include <fstream>
using namespace std;
//定義學生類
class Student
{
public:
    //宣告必要的成員函式
    Student() {}
    ~Student();
    double gettotal();
    static int getstu_num();
    static double gettotal_sum();
    friend ostream& operator <<(ostream &out,Student &s);
    friend istream& operator >>(istream &in,Student &s);
    bool pass();
private:
    string name;
    double cpp;
    double math;
    double english;
    double total;
    static int stu_num;  //學生人數，處理為類的靜態成員合適
    static double total_sum; //學生總分和
};
 int Student::stu_num=0;
 double Student::total_sum=0;
Student::~Student()
{
    total_sum=total;
    stu_num--;
}
double Student::gettotal()
{
    return total;
}
 int Student::getstu_num()
{
    return stu_num;
}
 double Student::gettotal_sum()
{
    return total_sum;
}
ostream& operator <<(ostream &out,Student &s)
{
    out<<s.name<<"\t"<<s.cpp<<"\t"<<s.math<<"\t"<<s.english<<"\t"<<s.total;
    return out;
}
 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++;
    Student::total_sum+=s.total;
    return in;
}
bool Student::pass()
{
    return cpp>=60 && math>=60 && english>=60;
}

int main( )
{
    Student stud[200],t; //stud[200]為儲存資料的物件陣列
    string sname;
    double total_avg;
    int i=0;
    //從檔案score.dat中讀入資料，儲存到物件陣列中
    ifstream infile("score.dat",ios::in);
    if(!infile)
    {
        cerr<<"error"<<endl;
        exit(1);
    }
    while(!infile.eof())
        infile>>stud[i++];
    infile.close();
    //總分高於平均總分且沒掛科的同學的資訊儲存到檔案pass_score.dat中
    if(Student::getstu_num()>0)
    {
        total_avg = Student::gettotal_sum() / Student::getstu_num();
        ofstream outfile("pass_score.dat",ios::out);
        if(!outfile)
        {
            cerr<<"open error!"<<endl;
            exit(1);
        }
        for(i=0; i<Student::getstu_num(); i++)
        {
            if(stud[i].gettotal()>total_avg&&stud[i].pass())
            {
                outfile<<stud[i]<<endl;
            }
        }
        outfile.close();
        cout<<"請去檔案中檢視"<<endl;
    }
    return 0;
}