如果 else 语句和 while 循环

本文关键字：while 循环 语句 else 如果 | 更新日期: 2023-09-27 18:37:22

请看下面的代码

namespace Funny
{
    class QuesionsAndAnswers
    {
        private double firstNumber;
        private double secondNumber;
        private double userAnswer;
        private double computerAnswer;
        private string operators;
        private bool answerCorrect;
        private bool enableDouble;
        private double[] listOfNumbers;
        private string[] listOfOperators;
        private Random randomizer;
        private static QuesionsAndAnswers qa;
        private QuesionsAndAnswers()
        {
            randomizer = new Random();
            listOfNumbers = new double[] { 1,2,3,4,5,6,7,8,9 };
            listOfOperators = new string[] { "+", "-", "*", "/" };
        }
        public static QuesionsAndAnswers getQuesionsandAnswersInstance()
        {
            if (qa == null)
                qa = new QuesionsAndAnswers();
             return qa;
        }
        public string generateQuestions()
        {
            string result = "";
            operators = listOfOperators[randomizer.Next(listOfOperators.Length)];
            firstNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
            secondNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
            if ((operators.Equals("/")) && (enableDouble == false))
            {
                while (firstNumber % secondNumber == 0)
                {
                    firstNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
                }
                result = firstNumber + operators + secondNumber;
            }
            else if (operators.Equals("-") && (firstNumber<secondNumber))
            {
                while (firstNumber > secondNumber)
                {
                    firstNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
                    secondNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
                }
                result = firstNumber + operators + secondNumber;
            }
            return result;
        }
        public void setDoubleAnswers(bool check)
        {
            enableDouble = check;
        }
    }
}

在这里，在 generateQuestions（） 方法中，我正在尝试生成一些数学问题。

如果运算符在"-"中，并且如果第一个数字<第二个数字，则应重新生成数字（第一个数字和第二个数字）以确保答案不是减号值。>

而且，如果运算符为"/"并且布尔值为 false，则应再次重新生成数字以确保答案（这意味着计算，例如 2/1 = 2）不包含任何浮点（这意味着它不应该生成像 2/3 这样的问题，因为答案包含浮点）。

在我的尝试中，以上两者都没有发生。它仍然会产生意想不到的答案，或者有时什么都没有。为什么？请帮忙

请注意，我是一名 Java 开发人员，这是我的第一个主要 C# 项目。

如果 else 语句和 while 循环

好吧，它有时什么也不返回，因为除了您捕获的边缘情况之外，您从未将result设置为""以外的任何内容。

而且你的while陈述都是错误的。它应该是：

while ((firstNumber % secondNumber) != 0)
:
while (firstNumber < secondNumber)

但是，为了提高效率，我不会做第二while因为您可能会在该属性所在的位置获得长时间的对。如果数字是错误的，只需交换它们。

而且在极少数情况下，你的数字选择中的余数将为零（9/3、8/4、8/2、6/3、6/2、4/2、M/M和N/1（我认为）是详尽的列表）。如果你想要一组更扩展的方程，我会走另一条路，选择两个数字来多，然后将第一个与结果交换。

例如，给定两个数字 a = 3 和 b = 7 ，只需执行以下操作：

a = a * b;

并且您有a = 21, b = 7保证给出积分乘数并"21 / 7"提供方程式。

所以这个（伪代码）是我要开始的：

# Get the random values.
op = random_from ("+-/*")
n1 = random_from ("123456789")
n2 = random_from ("123456789")
# For subtraction, make sure n1 >= n2.
if op = "-" and n1 < n2:
    tmp = n1;
    n1 = n2;
    n2 = tmp;
# For division, make sure n1 is integral multiplier of n2.
if op = "/":
    n1 = n1 * n2
# Return expression in ALL cases.
return n1 + op + n2

while (firstNumber % secondNumber == 0)

应该是 

while (firstNumber % secondNumber != 0)

只要您提供的条件true，while循环就会继续执行。 由于您希望第一个数字 % 第二个数字等于 0;您应该循环并生成新值，只要firstNumber % secondNumber != 0 .

我相信你在减法循环方面也有同样的问题。

最后（与您的问题无关），您可以使用==来比较 C# 中的字符串。

if ((operators == "/") && (enableDouble == false))

你在while语句中有错误的条件，你应该有恰恰相反的条件。此外，如果没有任何条件匹配，则不会为结果赋值，因此应将行result = firstNumber + operators + secondNumber;移出条件语句（或仅替换为简单返回）：

...
        if ((operators.Equals("/")) && (enableDouble == false))
        {
            while (firstNumber % secondNumber != 0) // <-- change here
            {
                firstNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
            }
        }
        // second condition was repearing while condition and that was redundant.
        else if (operators.Equals("-")) 
        {
            while (firstNumber < secondNumber) // <-- change here
            {
                firstNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
                secondNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
            }
        }
        return firstNumber + operators + secondNumber;

在这两种情况下，您的while条件都是错误的，您需要将其更改为

while (firstNumber % secondNumber != 0)

和

while (firstNumber < secondNumber)

这是我从您的问题中理解的解决方案。

if ((operators.Equals("/")) && (enableDouble == false))
    {
        while (firstNumber % secondNumber != 0)
        {
            firstNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
        }
        result = firstNumber + operators + secondNumber;
   }
            else if (operators.Equals("-") && (firstNumber<secondNumber))
            {
                while (firstNumber < secondNumber)
                {
                    firstNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
                    secondNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
                }
                result = firstNumber + operators + secondNumber;
            }
  1. 通过创建两个不同的测试项目来实现测试用例
  2. 使用包含这些测试用例的 MSVS 单元测试项目进行报告
    3. 报告测试覆盖率，在第
  3. 一种情况下考虑MCDC，在第二种情况下考虑总体覆盖率，并评论发现不同覆盖率指标的原因

对于下面的代码

    namespace Funny
    {
    class QuesionsAndAnswers
    {
        private double firstNumber;
        private double secondNumber;
        private double userAnswer;
        private double computerAnswer;
        private string operators;
        private bool answerCorrect;
        private bool enableDouble;
        private double[] listOfNumbers;
        private string[] listOfOperators;
        private Random randomizer;
        private static QuesionsAndAnswers qa;
        private QuesionsAndAnswers()
        {
            randomizer = new Random();
            listOfNumbers = new double[] { 1,2,3,4,5,6,7,8,9 };
            listOfOperators = new string[] { "+", "-", "*", "/" };
        }
        public static QuesionsAndAnswers getQuesionsandAnswersInstance()
        {
            if (qa == null)
                qa = new QuesionsAndAnswers();
             return qa;
        }
        public string generateQuestions()
        {
            string result = "";
            operators = listOfOperators[randomizer.Next(listOfOperators.Length)];
            firstNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
            secondNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
            if ((operators.Equals("/")) && (enableDouble == false))
            {
                while (firstNumber % secondNumber == 0)
                {
                    firstNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
                }
                result = firstNumber + operators + secondNumber;
            }
            else if (operators.Equals("-") && (firstNumber<secondNumber))
            {
                while (firstNumber > secondNumber)
                {
                    firstNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
                    secondNumber = listOfNumbers[randomizer.Next(listOfNumbers.Length)];
                }
                result = firstNumber + operators + secondNumber;
            }
            return result;
        }
        public void setDoubleAnswers(bool check)
        {
            enableDouble = check;
        }
    }
    }
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