用一组学生和他们各自的GPA计算GPA的各种方法

Question

关于我正在研究的问题，我要给出更多的细节，具体的任务是：

编写一个计算所有学生平均、最低、最高和平均绩点的程序。首先，程序将读取学生记录(姓名和GPA)并确定文件中学生记录的数量。在获得所有的名称和GPA之后，您的程序将按GPA的升序对学生GPA和名称进行排序。最后，您的程序将: 1)显示所有的名称和GPA；2)确定和显示GPA的最小和最大值(有相应的学生名称)；3)计算和显示平均GPA。

这里是我作为成品拥有的东西：

//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;
}

然而，收到了以下错误，并且无法自己解决这些问题：

在函数'int ()‘中：

-WaddressSolved`

• 32:23:警告:语句没有效果，-Wunused-valueSolved`

• 35:12:警告:语句是引用，而不是调用，而不是调用，若要运行“-WaddressSolved`

• 35:12：”-Wunused-valueSolved`

• 43:17:警告:语句没有影响-Wunused-valueSolved`

• 43:17:错误：“名称”未在此作用域中声明，则

• 43:32: error: GPA：'GPA‘未在此作用域中声明，

• 48:21:警告:语句是引用，而不是调用，-WaddressSolved`

• 48:21:警告:语句不影响-Wunused-valueSolved`

• 51:12:错误:无法在assignmentSolved

中将'double(const *，int)‘转换为'displayMinMaxGPA’

将非常感谢您的任何帮助，谢谢提前

"`“错误通过调用函数并将参数放入

"“错误通过调用calcAvgGPA函数后在括号中放置参数来解决。

Answer 1

你在基本理解上有几个大错误。让我们仔细研究一下，看看我们能帮助我们了解些什么。另外，您使用的是std::string，但不使用std::vector (这将使整个分配更容易)。

此外，(2)免责声明，我还没有看过任何函数中的逻辑，看它们是否正确工作.一旦这为您构建，您可以工作，以使逻辑正确，如果它是错误的。

修正了scope. CoryKramer提到的错误(您已经编辑了问题以表明您有)，

• 您没有在主函数
• 中声明GPA或name对象，因为您没有使用类，并且没有任何成员数据，您需要将这些信息存储在main
• 中。

1. 您的函数不接受对其参数的引用，而是通过复制

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这个作用域(或全局范围)中不存在的2个变量。您需要在main的作用域中声明这些变量，如果在可以编辑这些变量的作用域中没有这些变量，则不同的函数将无法使用相同的变量。

以复制方式获取项目与以参考方式获取

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

在这个原型中，通过引用参数students，这意味着可以更新main作用域中的变量。但是你不是通过引用其他任何参数，而是通过复制。注意到丢失的&了吗？即使在main作用域中有这些变量，它们也不会被更新，因为函数在其作用域中复制和使用这些副本，而不是在更高的作用域中修改变量。您的所有函数本质上都存在此错误。考虑哪些函数需要输入，哪些变量需要修改，哪些变量不需要修改。

也是

我有一种感觉，你会遇到更大的问题与动态数组大小。我可以看到这一点，因为我没有看到new实例用于GPA或name变量。这是一个std::vector将真正闪耀的地方，但我将由你来完成(因为这是一项家庭作业)。