using System;

using System.Collections.Concurrent;

​

public class Program

{

    public static class Memory

    {

        public static ConcurrentDictionary<string, long> GradeRank;

    }

​

    public static void Initialize()

    {

        Memory.GradeRank = new ConcurrentDictionary<string, long>();

        Memory.GradeRank.TryAdd("A", 80);

        Memory.GradeRank.TryAdd("B", 70);

        Memory.GradeRank.TryAdd("C", 60);

        Memory.GradeRank.TryAdd("D", 50);

        Memory.GradeRank.TryAdd("E", 40);

    }

​

    public static void Main()

    {

        Initialize();

        var quit = false;

        while (!quit)

        {

            try {

                Console.WriteLine("Input operation command:");

                string input = Console.ReadLine();

                if (input.Length == 0)

                {

                    Console.WriteLine("A Grade: >={0}\nB Grade: >={1}\nC Grade: >={2}\nD Grade: >={3}\nFail: <{3}", GetScore("A"), GetScore("B"), GetScore("C"), GetScore("D"));

                }

                else if (input.Trim() == "q")

                {

                    quit = true;

                }

                else

                {

                    string[] args = input.Split(',');

                    double[] doubleArgs = Array.ConvertAll(args, s => double.Parse(s));

                    //Compute average score

                    double avg = ComputeAverage(doubleArgs);

                    Console.WriteLine("Your average score is: " + avg + '\n');

                    //Display the letter grade for each score entered

                    string[] grades = GetLetterGrades(doubleArgs);

                    Console.WriteLine("Letter grade for each score entered: [" + string.Join(",", grades) + "]" +'\n');

                    //Display the grades in descending order

                    string[] sortedoutput = BubbleSort(doubleArgs, "s");

                    Console.WriteLine("Score sorted in descending order: [" + string.Join(",", sortedoutput) + "]" + '\n');

​

                }

            } catch (Exception ex)

            {

            }

        }

    }

​

    public static double GetScore(String grade)

    {

        double score = 0;

        if (Memory.GradeRank.ContainsKey(grade))

        {

            score = Memory.GradeRank[grade];

        }

​

        return score;

    }

​

    public static double ComputeAverage(double[] scoreArray)

    {

        double average = 0;

        //Write your logic to compute average score

        int i = 0;

        double sum = 0;

        for (i = 0; i < scoreArray.Length; i++)

        {

            sum += scoreArray[i];

        }

​

        average = (double)sum / scoreArray.Length;

        return average;

    }

    public static string[] GetLetterGrades(double[] scoreArray)

    {

        string[] letterGrades = new string[scoreArray.Length];

        //Write your logic to list the letter grade for each score entered

        int i = 0;

        for (i = 0; i < scoreArray.Length; i++)

        {

            if (scoreArray[i] >= 0 && scoreArray[i] <50)

            {

                letterGrades[i] = "E";

            }

            else if (scoreArray[i] >= 50 && scoreArray[i] <60)

            {   

                letterGrades[i] = "D";

            }

            else if (scoreArray[i] >= 60 && scoreArray[i] <70)

            {

                letterGrades[i] = "C";

            }

            else if (scoreArray[i] >= 70 && scoreArray[i] <60)

            {

                letterGrades[i] = "B";

            }

            else if (scoreArray[i] >= 80)

            {

                letterGrades[i] = "A";

            }

        }

        return letterGrades;

    }

    public static string[] BubbleSort(double[] scoreArray, string method)

    {

        string[] output;

        //Write your logic to sort the grades using bubble sort

        double temp; 

        for (int p = 0; p <= scoreArray.Length - 2; p++)

            {

                for (int i = 0; i <= scoreArray.Length - 2; i++)

                {

                    if (scoreArray[i] > scoreArray[i + 1])

                    {

                        temp = scoreArray[i + 1];

                        scoreArray[i + 1] = scoreArray[i];

                        scoreArray[i] = temp;

                    }

                } 

            }

        return output = Array.ConvertAll(scoreArray, s => s.ToString());

    }

}