c++ - 使用一组学生及其各自的 GPA 对 GPA 进行各种计算

Question

为了更详细地说明我正在处理的问题，确切的任务是:

编写一个程序，计算平均值、最小值、最大值和
所有学生的平均 GPA。首先，你的程序会读入学生记录
(姓名和 GPA)并确定文件中学生记录的数量。毕竟
获得姓名和 GPA 后，您的程序将对学生 GPA 和
按 GPA 升序排列的名称。最后，您的程序将，1)显示所有名称
和 GPA，2) 确定并显示最小和最大 GPA(带有
对应的学生姓名)，以及 3)计算并显示平均 GPA。

这是我的成品:

//gpaCalc.cc                                                                                                                                                                                   
//Author: O'Brien Little                                                                                                                                                                       
//Purpose: To calculate and display the average, minimum and maximum GPA for some U of L students, where the GPA's and student names are read from
//an input file and are stored as arrays 
//Inputs: GPA's of several students, student names                                                                                                                                                          
//Outputs: Average, minimum and maximum GPA of the collection of students, along with the corresponding student names
//and display a list of all students and their respective GPA's
//Assumptions: Max 50 Students' information

#include<iostream>
#include<fstream>
#include<string>
using namespace std;

const int arraySize=50; //Upper limit on the number of students and GPA's

//Function prototypes
void obtainNamesAndGPAs(double GPA[], string name[], int &students);
void sortGPA(double GPA[], string name[], int students);
void displayMinMaxGPA(const double GPA[], const string name[], int students);
double calcAvgGPA(const double GPA[], int students);



int main()
{
    //Variable declarations
    double AvgGPA;
    int index=0, students;

    //Reading the names of the students and their corresponding GPAs and storing them in an array
    obtainNamesAndGPAs;

    //Sorting the students GPAs in assending order allong with the corresponding student names
    sortGPA;

    //Displaying all the names of the students and their GPAs
    cout << "Here is a list of all the students and their GPAs that were entered into te system: " << endl;

    //While loop to display all the students and their GPAs
    while(index<students)
    {
        cout << name[index] << GPA[index];
        index++;
    }

    //Displaying the lowest and the highest GPAs and the students that achieved those
    displayMinMaxGPA;

    //Calculating the average GPA of the collection
    AvgGPA = calcAvgGPA;

    //Displaying the average GPA to the user
    cout << "The average GPA of the collection of students was: " << AvgGPA << endl;

    //End program
    return 0;
}

//****************************************************************                                                                                                                             
//Function: obtainNamesAndGPAs                                                                                                                                                                        
//Purpose: To obtain the names and GPAs of the students                                                                                                                                
//Input: GPA[], name[], &students                                                                                                                                                             
//Return Value: Void                                                                                                                                                                           
//Assumtions: None                                                                                                                                            
//****************************************************************  
void obtainNamesAndGPAs(double GPA[], string name[], int &students)
{
    //Array access variable
    int indexn=0, indexg=0; 

    //File stream declaration
    ifstream inFile;

    //Opening the input file and read in the first value
    inFile.open("GPA.txt");
    inFile >> name[indexn];

    //While loop to gather the GPAs from the file and insert them into their corresponding array index
    while(!inFile.eof() && indexn < arraySize)
    {
        indexn++;
        inFile >> GPA[indexg];
        indexg++;
        inFile >> name[indexn];
        students++;
    }
    //End of function
    return;
}

//****************************************************************                                                                                                                             
//Function: sortGPA                                                                                                                                                                       
//Purpose: To sort students (and thier corresponding GPAs 
//in assending order
//Input: GPA[], name[], students                                                                                                                                                            
//Return Value: Void                                                                                                                                                                           
//Assumtions: None                                                                                                                                            
//****************************************************************  
void sortGPA(double GPA[], string name[], int students)
{
    //Variable declarations
    double temporaryg;
    int first, second;
    string temporaryn;

    //Sorting the GPAs by asscending order
    //For loop to indicate the first value of the GPA array
    for(first=0;first<students;first++)
    {       
        //For loop to indicate the following value in the GPA array to check 
        for(second=first+1;second<students;second++)
        {
            //If statement to make sure the GPA and name array are in asscending order and 
            //ensures the student name stays with the GPA
            if(GPA[first]>GPA[second])
            {
                //Storing the bigger GPA and name for later
                temporaryg=GPA[first];
                temporaryn=name[first];
                //Making it so the smaller GPA and name comes first
                GPA[first]=GPA[second];
                name[first]=name[second];
                //Making the lower GPA and name come second
                GPA[second]=temporaryg;
                name[second]=temporaryn;
            }
        }
    }

    //End of function
    return;
}

//****************************************************************                                                                                                                             
//Function: displayMinMaxGPA                                                                                                                                                                      
//Purpose: To display the Min and Max GPA and their students
//Input: GPA[], name[], students                                                                                                                                                            
//Return Value: Void                                                                                                                                                                           
//Assumtions: None                                                                                                                                            
//**************************************************************** 
void displayMinMaxGPA(const double GPA[], const string name[], int students)
{
    //Variable declaration
    //initialized to extreme values to ensure they will be taken by the array values
    double Maxg=0, Ming=10;
    int index;
    string Maxn, Minn;

    //For loop to find the Max and Min GPA in the array and find the corresponding 
    //students name
    for(index=0;index<students;index++)
    {
        if(GPA[index]>Maxg)
        {
            Maxg=GPA[index];
            Maxn=name[index];
        }
        else if(GPA[index]<Ming)
        {
            Ming=GPA[index];
            Minn=name[index];
        }
        else
        {
            break;
        }
    }

    //Displaying the Min and Max GPA and the corresponding students to the user
    cout << "The minimum GPA that was entered belonged to: " << Ming << " and was: " << Minn << endl;
    cout << "The maximum GPA that was entered belonged to: " << Maxg << " and was: " << Maxg << endl;

    //End of function
    return;
}

//****************************************************************                                                                                                                             
//Function: calcAvgGPA                                                                                                                                                                   
//Purpose: To calculate the average GPA
//Input: GPA[], students                                                                                                                                                            
//Return Value: AvgGPA                                                                                                                                                                           
//Assumtions: None                                                                                                                                            
//**************************************************************** 
double calcAvgGPA(const double GPA[], int students)
{
    //Variable declarations
    double sum, AvgGPA;
    //Index set to zero to make sure the array starts in the first position
    int index=0;

    //While loop to take each individual GPA out of the array and add it to sum
    while(index<students)
    {
        sum = sum + GPA[index];
        index++;
    }

    //Calculating the average GPA
    AvgGPA = sum/students;


    //End of function and return AvgGPA
    return AvgGPA;
}

但是，我收到以下错误，我无法自行解决:

在函数'int main()'中:

32:23:警告:语句是对函数的引用，而不是调用
'obtainNamesAndGPA' [-Waddress] 已解决`

32:23:警告:语句无效 [-Wunused-value] 已解决`

35:12:警告:语句是对函数的引用，而不是调用
'sortGPA' [-Waddress] 已解决`

35:12:警告:语句无效 [-Wunused-value] 已解决`

43:17:错误:未在此范围内声明“名称”

43:32:错误:未在此范围内声明“GPA”

48:21:警告:语句是对函数的引用，而不是调用
'displayMinMaxGPA' [-Waddress] 已解决`

48:21:警告:语句无效 [-Wunused-value] 已解决`

51:12:错误:无法将 'double(const double*, int)' 转换为 'double'
在任务中解决了``

任何帮助将不胜感激，在此先感谢

"`"错误通过调用函数并将参数放入

调用 calcAvgGPA 函数后，通过将参数放在括号中解决了 "``"错误

Answer 1

您在基本理解上存在一些大错误。让我们通过它们，看看我们可以帮助启发什么。此外，您正在使用 std::string 但未使用 std::vector (这将使整个任务更容易)。
还有(2) 免责声明 ，我还没有查看任何函数中的逻辑以查看它们是否可以正常工作......一旦为您构建，您可以努力使逻辑正确，如果它是错误的。

修复 CoryKramer 提到的错误(您已编辑您的问题以建议您有)

您没有在主函数中声明 GPA 或名称对象

由于您没有使用类并且没有任何成员数据，因此您需要将此信息存储在 main 中。范围。

您的函数不引用它们的参数，您通过复制

获取它们

不声明变量

    //Displaying all the names of the students and their GPAs
    cout << "Here is a list of all the students and their GPAs that were entered into te system: " << endl;

    //While loop to display all the students and their GPAs
    while(index<students)
    {
        cout << name[index] << GPA[index];  // <--- This line
        index++;
    }

上面提到的行试图引用此范围(或全局范围)中不存在的 2 个变量。您需要在 main 中声明这些变量的范围。如果您在可以编辑它们的范围内没有这些变量可用，则不同的函数将无法使用相同的变量。

通过复制与通过引用获取项目

//Function prototypes
void obtainNamesAndGPAs(double GPA[], string name[], int &students);

在这个原型(prototype)中，您使用参数 students通过引用，这意味着 main 中的变量范围可以更新。但是您不是通过引用而是通过复制来获取任何其他参数。注意丢失的 & ?即使您在 main 中有这些变量范围，它们不会得到更新，因为函数会复制并在其范围内使用这些拷贝，而不是在更高范围内修改变量。
您的所有功能本质上都有此错误。
想想函数需要输入什么，哪些变量需要修改，哪些变量不需要。

还
我有一种感觉，你会遇到动态数组大小的更大问题。我可以看到这个，因为我看不到 new GPA 的实例或 name变量。这是 std::vector 真的会发光，但我会把它留给你来完成(因为这是一项家庭作业)。