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c++ - 使用一组学生及其各自的 GPA 对 GPA 进行各种计算

问题描述

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，计算所有学生的平均、最低、最高和平均 GPA。首先，您的程序将读入学生记录（姓名和 GPA）并确定文件中学生记录的数量。获得所有姓名和 GPA 后，您的程序将按 GPA 升序对学生 GPA 和姓名进行排序。最后，您的程序将，1) 显示所有姓名和 GPA，2) 确定并显示最小和最大 GPA（以及相应的学生姓名），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，我无法自行解决这些问题：

在函数'int main()'中：

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

标签： c++arrayscompiler-errorsuser-defined-functions

解决方案

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（这将使整个分配更容易）。

另外（2）免责声明，我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，如果逻辑错误，您可以努力使逻辑正确。

  1. 修复 CoryKramer 提到的错误（您已编辑问题以建议您有）
  2. 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范围中。
  3. 您的函数不引用它们的参数，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++;
    }

上述行试图引用此范围（或全局范围）中不存在的 2 个变量。您需要在main的范围内声明这些变量。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);

在此原型中，您students通过引用获取参数，这意味着main可以更新范围内的变量。但是您不是通过引用而是通过复制来获取任何其他参数。注意到失踪了&吗？即使您在main范围内有这些变量，它们也不会随着函数复制并在其范围内使用这些副本而不是在更高范围内修改变量而得到更新。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。我可以看到这一点，因为我看不到任何new实例GPA或name变量。这是 astd::vector真正闪耀的地方，但我会留给你来完成（因为这是一项家庭作业）。

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