c# - 当我使用 Math.Round() 时，它总是返回下限

Question

这个问题已经有答案了:

How can I force division to be floating point? Division keeps rounding down to 0? (11 个回答)

已关闭 3 年前。

我正在制作一个数学项目，用户根据他们选择的难度级别回答问题!

但每次问题是除法问题时，它都会返回下界。

例如，如果代码询问“5/3”是什么，答案应该是 2，但代码认为正确答案是 1。

这是我的代码:

using System;

namespace mathstester
{
    class Program
    {
        enum UserDifficulty
        {
            Easy,
            Normal,
            Hard
        }
        public static void Main(string[] args)
        {
            string userDifficulty = "";
            do
            {
                Console.WriteLine("What difficulty level would you like to do! Please type E for Easy, N for Normal and H for hard");
                userDifficulty = Console.ReadLine().ToUpper();
            } while (userDifficulty != "E" && userDifficulty != "N" && userDifficulty != "H");

            int numberOfQuestions = 0;
            do
            {
                Console.Write("How many questions would you like to answer? Please type a number divisible by 10!");
                int.TryParse(Console.ReadLine(), out numberOfQuestions);
            } while (numberOfQuestions % 10 != 0);

            int numberOfQuestionsLeft = numberOfQuestions;
            Random random = new Random();
            int score = 0;

            while (numberOfQuestionsLeft > 0)
            {
                var operation = random.Next(1, 7);
                int number1 = 0;
                int number2 = 0;
                switch (userDifficulty)
                {
                    case "E":
                        switch (operation)
                        {
                            case 1:
                                number1 = random.Next(1000);
                                number2 = random.Next(1000);
                                break;
                            case 2:
                                number1 = random.Next(1000);
                                number2 = random.Next(1000);
                                break;
                            case 3:
                                number1 = random.Next(13);
                                number2 = random.Next(13);
                                break;

                        }
                        break;
                    case "N":
                        switch (operation)
                        {
                            case 1:
                                number1 = random.Next(1000);
                                number2 = random.Next(1000);
                                break;
                            case 2:
                                number1 = random.Next(1000);
                                number2 = random.Next(1000);
                                break;
                            case 3:
                                number1 = random.Next(1000);
                                number2 = random.Next(1000);
                                break;
                            case 4:
                                number1 = random.Next(1, 10000);
                                number2 = random.Next(1, 1000);
                                break;

                        }
                        break;
                    case "H":
                        switch (operation)
                        {
                            case 3:
                                number1 = random.Next(1000);
                                number2 = random.Next(1000);
                                break;
                            case 4:
                                number1 = random.Next(1, 10000);
                                number2 = random.Next(1, 1000);
                                break;
                            case 5:
                                number1 = random.Next(13);
                                number2 = random.Next(5);
                                break;
                            case 6:
                                number1 = random.Next(1000);
                                break;

                        }
                        break;
                }

                if(operation == 1 && (userDifficulty == "E" || userDifficulty == "N"))
                {
                    Console.Write($"What is {number1} + {number2} =");
                    int correctAnswer = number1 + number2;
                    int userAnswer = Convert.ToInt32(Console.ReadLine());
                    if (correctAnswer == userAnswer)
                    {
                        Console.WriteLine("Well Done!");
                        score++;
                    }
                    else
                    {
                        Console.WriteLine("Your answer is incorrect!");
                    }
                    numberOfQuestionsLeft--;
                }
                else if (operation == 2 && (userDifficulty == "E" || userDifficulty == "N"))
                {
                    Console.Write($"What is {number1} - {number2} =");
                    int correctAnswer = number1 - number2;
                    int userAnswer = Convert.ToInt32(Console.ReadLine());
                    if (correctAnswer == userAnswer)
                    {
                        Console.WriteLine("Well Done!");
                        score++;
                    }
                    else
                    {
                        Console.WriteLine("Your answer is incorrect!");
                    }
                    numberOfQuestionsLeft--;
                }
                else if (operation == 3 && (userDifficulty == "E" || userDifficulty == "N" || userDifficulty == "H"))
                {
                    Console.Write($"What is {number1} * {number2} =");
                    int correctAnswer = number1 * number2;
                    int userAnswer = Convert.ToInt32(Console.ReadLine());
                    if (correctAnswer == userAnswer)
                    {
                        Console.WriteLine("Well Done!");
                        score++;
                    }
                    else
                    {
                        Console.WriteLine("Your answer is incorrect!");
                    }
                    numberOfQuestionsLeft--;
                }
                else if (operation == 4 && (userDifficulty == "N" || userDifficulty == "H") && (number1 > number2))
                {
                    Console.Write($"To the nearest integer, What is {number1} / {number2} =");
                    double correctAnswer = (number1 / number2);
                    double roundedCorrectAnswer = Math.Round(correctAnswer);
                    int userAnswer = Convert.ToInt32(Console.ReadLine());
                    if (roundedCorrectAnswer == userAnswer)
                    {
                        Console.WriteLine("Well Done!");
                        score++;
                    }
                    else
                    {
                        Console.WriteLine("Your answer is incorrect!");
                    }
                    numberOfQuestionsLeft--;
                }
                else if (operation == 5 && userDifficulty == "H")
                {
                    Console.Write($"What is {number1} ^ {number2} =");
                    double correctAnswer = Math.Pow(number1, number2);
                    int userAnswer = Convert.ToInt32(Console.ReadLine());
                    if (correctAnswer == userAnswer)
                    {
                        Console.WriteLine("Well Done!");
                        score++;
                    }
                    else
                    {
                        Console.WriteLine("Your answer is incorrect!");
                    }
                    numberOfQuestionsLeft--;
                }
                else if (operation == 6 && userDifficulty == "H")
                {
                    Console.Write($"To the nearest integer, What is √{number1} =");
                    double correctAnswer = Math.Sqrt(number1);
                    double roundedCorrectAnswer = Math.Round(correctAnswer);
                    int userAnswer = Convert.ToInt32(Console.ReadLine());
                    if (roundedCorrectAnswer == userAnswer)
                    {
                        Console.WriteLine("Well Done!");
                        score++;
                    }
                    else
                    {
                        Console.WriteLine("Your answer is incorrect!");
                    }
                    numberOfQuestionsLeft--;
                }
            }
            Console.WriteLine($"You got a score of {score} out of {numberOfQuestions}");
        }
    }
}

发生的情况是这样的:

Answer 1

由于 number1 和 number2 是整数，因此可以使用 integer division 将它们相除。 ，并且只保留结果的“整个”部分(即小数点左边的部分)。

在执行除法之前，您可以将它们(或至少其中一个)转换为 double 以获得“正确”的结果:

double correctAnswer = ((double) number1) / number2;