第十六周项目2-文件保存学生名单

来源：互联网发布：招商银行黄金分析软件编辑：程序博客网时间：2024/05/22 03:10

问题及代码：

/* *Copyright (c) 2016，烟台大学计算机学院 *All rights reserved. *文件名称：zwj.cpp *作    者：张伟晶 *完成日期：2016年6月20日 *版 本 号：v1.0 * *问题描述：用文件保存学生信息*输入描述： *程序输出： */  #include <fstream>#include<iostream>#include<string>#include<cstdlib>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++;       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;}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;     ifstream infile("score.txt",ios::in);    if(!infile)         {        cerr<<"open error!"<<endl;        exit(1);    }    while(!infile.eof())    {        infile>>stud[i++];       }    infile.close();    if(Student::get_stu_num()>0)    {        total_avg = Student::get_total_sum() / Student::get_stu_num();        ofstream outfile("pass_score.txt",ios::out);        if(!outfile)        {            cerr<<"open error!"<<endl;            exit(1);        }        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();        cout<<"请到文件pass_score.dat中查看名单："<<endl;    }    return 0;}

运行结果：

知识点总结：

静态常量的定义不能在类内，必须在类外。

int Student::stu_num = 0;double Student::total_sum = 0;

0 0