目录

题目

代码

运行命令（在控制台输入）

运行截图

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题目

（修改GradeBook）修改图5.9~图5.11所示的 GradeBook 程序，使它计算一组成绩的平均成绩。
成绩A为4分，成绩B为3分，依次类推。
A:4
B:3
C:2
D:1
E:0
F:-1

代码

注意有注释的位置，基本都是有修改的地方。

//5_15.h

// GradeBook.h

#include <string>

class GradeBook
{
public:
	GradeBook(std::string);
	void setCourseName(std::string);
	std::string getCourseName() const;
	void setCourseTeacher(std::string);
	std::string getCourseTeacher() const;
	void displayMessage() const;
	void inputGrades();
	void displayGradeReport() const;

private:
	std::string courseName;
	unsigned int aCount;
	unsigned int bCount;
	unsigned int cCount;
	unsigned int dCount;
	unsigned int eCount;
	unsigned int fCount;
	double gradeSum;//增加了存储分数和的变量
};

//5_15.cpp

#include <iostream>
#include "5_15.h"
#include <iomanip>
using namespace std;

GradeBook::GradeBook(string name) : aCount(0), bCount(0), cCount(0), dCount(0), eCount(0), fCount(0)
{
    setCourseName(name);
}

void GradeBook::setCourseName(string name)
{
    if (name.size() <= 25)
        courseName = name;
    else
    {
        courseName = name.substr(0, 25);
        cerr << "name\"" << name << "\"exceeds maximum length(25).\n"
             << "Limiting courseName to first 25 characters.\n"
             << endl;
    }
}

string GradeBook::getCourseName() const
{
    return courseName;
}

void GradeBook::displayMessage() const
{
    cout << "Welcome to the grade book for " << getCourseName() << endl;
}

void GradeBook::inputGrades() // 有修改
{
    int grade;
    gradeSum = 0.0; // 初始化
    cout << "Enter the letter grades:" << endl
         << "Enter the EOF character to end input." << endl;

    while ((grade = cin.get()) != EOF)
    {
        switch (grade)
        {
        case 'A':
        case 'a':
            aCount++;
            gradeSum += 4; // 添加每个字母对应的分数
            break;

        case 'B':
        case 'b':
            bCount++;
            gradeSum += 3;
            break;

        case 'C':
        case 'c':
            cCount++;
            gradeSum += 2;
            break;

        case 'D':
        case 'd':
            dCount++;
            gradeSum += 1;
            break;

        case 'E':
        case 'e':
            eCount++;
            gradeSum += 0;
            break;

        case 'F':
        case 'f':
            fCount++;
            gradeSum += (-1);
            break;

        case '\n':
        case '\t':
        case ' ':
            break;

        default:
            cout << "Incorrect letter grade entered."
                 << "\nPlease enter a new grade." << endl;
            break;
        }
    }
}

void GradeBook::displayGradeReport() const//有修改
{
    int count;
    cout << "\n\nNumber of students who received each letter grade:"
         << "\nA:" << aCount << "\nB:" << bCount << "\nC:" << cCount
         << "\nD:" << dCount << "\nE:" << eCount << "\nF:" << fCount << endl;

    count = aCount + bCount + cCount + dCount + eCount + fCount;                      // 求一共有多少个字母
    cout << "这一组成绩的平均数:" << gradeSum / (static_cast<double>(count)) << endl; // 计算平均数
    ;
}

//5_15main.cpp

#include <iostream>
#include "5_15.h"
using namespace std;

int main()
{
    GradeBook myGradeBook("zhang san");

    myGradeBook.displayMessage();
    myGradeBook.inputGrades();
    myGradeBook.displayGradeReport();

    return 0;
}

运行命令（在控制台输入）

g++ 5_15main.cpp 5_15.cpp -o 5_15.exe

5_15.exe

注意：如果输入5_15.exe执行不了，可以尝试使用 ./5_15.exe (别忘记最开始的点)，我之前用这个命令执行的代码。

运行截图

最后，大家有问题欢迎一起交流，正在努力学习C++ ~~~