第十五周（项目二）——用文件保存学生的名单。

/*烟台大学计算机学院学生 *All right reserved. *文件名称:用文件保存学生的名单 *作者：何新新*完成日期：2014年6月5日 *版本号：v1.0 *对任务及求解方法的描述部分:用文件保存学生的名单 *我的程序：*/    #include <iostream>  #include <fstream>  #include <string>  #include<cstdlib>  using namespace std;    class Student  {    public:     double get_total();    // 求单个学生总分     int get_stu_num();  // 等到学生的数量     double get_total_sum();  // 所有学生总分和     bool pass(double );     friend istream &operator >>(istream &in,Student &s);     friend ostream &operator <<(ostream &out,Student &s);    private:     string name;     double cpp;     double math;     double english;     double total;     static int stu_num;   //学生人数，处理为类的静态静态成员合适     static double total_sum;  //学生总分和  };  double Student::total_sum=0;  double Student::get_total()  {     total=cpp+math+english;      return total;  }    int Student::stu_num=0;  int Student::get_stu_num()  {      return stu_num;  }    double Student::get_total_sum()  {      return total_sum;  }    bool Student::pass(double avg)  {      if(total>=avg&&(cpp>=60)&&(math>=60)&&(english>=60))        return true;     else        return false;  }    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.get_total()<<"\t";      return out;  }  int main()  {      Student stud[200],t;      double total_avg=0;      int i=0;      //string sname;      ifstream infile("score.txt",ios::in);      if(!infile)      {         cerr<<"date error!";         exit(0);      }      while(infile>>stud[i])      {          i++;      }      infile.close();        for(i=0;i<t.get_stu_num();i++)      {          double s=0;          s+=stud[i].get_total();          total_avg=s/t.get_stu_num();      }      ofstream outfile("pass_score.txt",ios::out);      if(!outfile)          {              cerr<<"open error!"<<endl;              exit(0);          }      for(i=0;i<t.get_stu_num();i++)      {          if(stud[i].pass(total_avg))           outfile<<stud[i]<<endl;      }      outfile.close();      cout<<"请到 pass_score 文件中检查。"<<endl;      return 0;  }   运行结果，如下图：

<img src="http://img.blog.csdn.net/20140606205922171?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvdTAxMjM3MDEzNg==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" alt="" />

 运行前文件：

<img src="http://img.blog.csdn.net/20140606205949000?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvdTAxMjM3MDEzNg==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" alt="" />