返回零的最小值[重复]

Posted 2023-03-17

【中文标题】返回零的最小值[重复]

【英文标题】：Minimum value returning zero [duplicate]

【发布时间】：2021-11-11 18:01:01

【问题描述】：

我有一个程序可以找到最低和最高等级。最大值函数有效，但最小值函数返回 0。我不确定我做错了什么，我的代码中没有错误。谢谢！

使用系统； 使用 System.Collections.Generic;

命名空间等级转换器 课堂节目 静态无效主要（字符串 [] 参数） bool doAgain = true; //float totalScore = 0 , averageScore; 字符串更多转换； int numberOfGrades;

        //Ask the user to enter their first and last name
        string userName = getName();

        //Print a welcome message: "Hello [first name] [last name] Welcome to the Grade Converter!"
        Console.WriteLine($"\nHello userName! Welcome to the Grade Converter!");

        while(doAgain)
            List<float> scores = new List<float>();

            //Prompt the user to enter the number of grades they need to convert "Enter the number of grades you need to convert: "
            numberOfGrades = getNumberOfGrades();

            //Prompt the user to enter the grades. The grades should be stored in a list and you should use the appropriate data type for the grades. 
            scores = populateGradesList(scores, numberOfGrades);
            
            //Print Grade Report
            printGradeReport(scores);
            printGradeStatistics(scores, numberOfGrades);
            float aveScore = getAverageGrade(scores);
            float maximumGrade = getMaximumGrade(scores);
            float minimumGrade = getMinimumGrade(scores);
            //averageScore = totalScore / numberOfGrades; 
            

            Console.WriteLine("Would you like to convert more grades (y/n)?");
            moreConversions = Console.ReadLine();

            //reset total score
            //totalScore = 0;

            if (moreConversions != "y" && moreConversions != "Y")
                doAgain = false;
            
        
    

    static float getMinimumGrade(List<float> listOfNumberGrades)
        float min = 0;;

        foreach(float grade in listOfNumberGrades)
            if( grade < min)
                min = grade;
            
        
        return min;
    

    static float getMaximumGrade(List<float> listOfNumGrades)
        float max = 0;

        foreach(float grade in listOfNumGrades)
            if( grade > max)
                max = grade;
            
            
        
            return max;
    

    static float getAverageGrade(List<float> listOfGrades)
        float total = 0;
        float average = 0;
        foreach(float grade in listOfGrades)
            total += grade;             
        
        average = total / listOfGrades.Count;
        return average;
        

    static void printGradeStatistics(List<float> listOfGrades, int numberOfGrades)
        float averageScore = getAverageGrade(listOfGrades);
        float maximumGrade = getMaximumGrade(listOfGrades);
        float minimumGrade = getMinimumGrade(listOfGrades);
        Console.WriteLine("\nGrade Statistics\n-------------------------\n");
        Console.WriteLine($"Number of grades: numberOfGrades");
        Console.WriteLine($"Average Grade: averageScore which is a getLetterGrade(averageScore)");
        Console.WriteLine($"Maximum Grade: maximumGrade");
        Console.WriteLine($"Minimum Grade: minimumGrade");
    

    static void printGradeReport(List<float> scoresList)
        string letterGrade;

        Console.WriteLine();
        foreach(float testScore in scoresList)
                //Convert the number grades to letter grades (A = 90-100, B = 80-89, C = 70-79, D = 60 - 69, F lower than 60)
            letterGrade = getLetterGrade(testScore);

                //Print all the numerical grades and their corresponding letter grades to the console 
            Console.WriteLine($"A score of testScore is a letterGrade grade");  
            
            return;

    

    static List<float> populateGradesList(List<float> listOfScores, int numGrades)
        float score;
        for(int counter = 0; counter < numGrades; counter ++)
                score = getScores();
                listOfScores.Add(score);
            
            return listOfScores;

    

    static int getNumberOfGrades()
        Console.WriteLine("\nEnter the number of grades you need to convert:");
        int numberOfGrades = int.Parse(Console.ReadLine());
        return numberOfGrades;
    

    static string getName()
        Console.WriteLine("Please enter your first name and last name");
        string userName = Console.ReadLine();
        return userName;
    

    static float getScores()
        float grade;
        while(true)
            Console.WriteLine("\nEnter the score to be converted: ");
            try
                grade = float.Parse(Console.ReadLine());
                break;  
            catch(FormatException)
                Console.WriteLine("Error: Only numbers allowed");
            
          
        return grade;
    

    static string getLetterGrade(float score)
        //(A = 90-100, B = 80-89, C = 70-79, D = 60 - 69, F lower than 60).
        if (score >= 90)
            return "A";
        else if(score >= 80)
            return "B";
        else if (score >= 70)
            return "C";
        else if(score >= 60)
            return "D";
        else
            return "F";
        
    

【问题讨论】：

getMinimumGrade 首先将最小值设置为 0。您需要做的是将起始最小值设置为集合中的第一个。

我怎么能做到这一点？ @尼尔

Debugging your code using the built-in Step Debugger 比你想象的要容易。

【参考方案1】：

您可以将起始值设置为列表中的第一个值。像这样的：

static float getMinimumGrade(List<float> listOfNumberGrades)
    float min = listOfNumberGrades.First();

    foreach(float grade in listOfNumberGrades)
        if( grade < min)
            min = grade;
        
    
    return min;

但请注意，如果列表中有 0 个项目，这将不起作用，而且它首先访问列表中的第一个项目。

更简单的方法是使用IEnumerable.Min:

static float getMinimumGrade(List<float> listOfNumberGrades)
    return listOfNumberGrades.Min();

【讨论】：

当我将 float min 更改为 listOfNumberGrades.First();我收到此错误消息：“List”不包含“First”的定义，并且找不到接受“List”类型的第一个参数的可访问扩展方法“First”（您是否缺少使用指令还是程序集引用？） [GradeConverter] @Neil

我修好了没关系，谢谢@Neil。