[英]How can I solve my StringBuilder problem?
我在做什么:使用StringBuilder
替換字符串中的變量以生成包含變化的問題。
string question;
void CreateNewQuestion()
{
Random rnd = new Random();
int questionNumber = rnd.Next(1, 4); //Generate a random question number
int a = rnd.Next(1, 10); //Create random numbers so the question is different each time
int b = rnd.Next(1, 15);
int c = rnd.Next(1, 15);
string q = questionNumber.ToString();
StringBuilder sbq = new StringBuilder("Question" +q);//StringBuilder is now called to replace the randomly called for question with its new variables
sbq.Replace("Question1", $"What is {a} + {a} ?");
sbq.Replace("Question2", $"What is {a} + {b} ?");
sbq.Replace("Question3", $"What is {a*c} + {a} ?"");
question = sbq.ToString();
}
問題:如果字符串q
(被修改的那個) = "Question1", StringBuilder.Replace
不會只停留在sb.Replace("Question1"...)
它仍然會計算問題 2 和 3。因此作為問題的數量增加了,因此效率低下。
問題:我如何創建包含變量的問題,以便以有效的方式在同一問題結構中提供變化?
我建議使用Dictionary<TKey, TValue>
:
Random rnd = new Random();
int questionNumber = rnd.Next(1, 4); //Generate a random question number
int a = rnd.Next(1, 10); //Create random numbers so the question is different each time
int b = rnd.Next(1, 15);
int c = rnd.Next(1, 15);
var questions = new Dictionary<int, string>
{
{ 1, "What is " + a + " + " + a + " ?" },
{ 2, "What is " + a + " + " + b + " ?" },
{ 3, "What is " + (a * b) + " + " + c + " ?" },
};
var question = string.Empty;
if (questions.TryGetValue(questionNumber, out question))
{
// key exists and you can read your question here
}
更新:
如果要在一個函數中創建字典而在另一個函數中創建隨機數,則必須有一個目標函數:
static Random rnd = new Random();
static void Main(string[] args)
{
int questionQuantity = 15;
var questions = new Dictionary<int, string>();
for (int i = 0; i < questionQuantity; i++)
{
int variableCount = rnd.Next(17);
var variables = CreateVariables(variableCount);
var signs = CreateSigns(variableCount - 1);
var question = CreateQuestion(variables, signs);
questions.Add(i, question);
}
}
以及其他功能:
public static List<int> CreateVariables(int variableQuantity)
{
var variables = new List<int>();
for (int i = 0; i < variableQuantity; i++)
{
variables.Add(rnd.Next(1, 15));
}
return variables;
}
public static List<char> CreateSigns(int variableQuantity)
{
var operators = new char[] {'+', '-', '/', '*' };
var randomOperators = new List<char>();
for (int i = 0; i < variableQuantity; i++)
{
randomOperators.Add(operators[ rnd.Next(0, 3) ]);
}
return randomOperators;
}
public static string CreateQuestion(List<int> variables, List<char> operations)
{
StringBuilder sb = new StringBuilder();
sb.Append("What is ");
for (int i = 0, j = 0; i < variables.Count; i++)
{
sb.Append(variables[i]);
if (i % 2 != 0)
{
sb.Append(" ");
sb.Append(operations[j]);
sb.Append(" ");
j++;
}
}
sb.Append("?");
return sb.ToString();
}
考慮使用 switch 語句
Random rnd = new Random();
int a = rnd.Next(1, 10); //Create random numbers so the question is different each time
int b = rnd.Next(1, 15);
int c = rnd.Next(1, 15);
string question;
switch (rnd.Next(1, 4)) {
case 1: {
question = "What is " + a + " + " + a + " ?";
break;
}
case 2: {
question = "What is " + a + " + " + b + " ?";
break;
}
case 3: {
question = "What is " + (a * b) + " + " + c + " ?";
break;
}
default: {
question = "Default Value";
break;
}
}
C# 8:
question = rnd.Next(1, 4) switch {
1 => "What is " + a + " + " + a + " ?",
2 => "What is " + a + " + " + b + " ?",
3 => "What is " + (a * b) + " + " + c + " ?",
_ => "Default Value"
};
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