/// <summary>
/// Generates a "choose matching string" question
/// </summary>
/// <param name="elementNumber">Amount of the elements in the generated
/// regular expression</param>
public ChooseMatchQuestion(int elementNumber)
{
//Generate the required regular expression
regex = RegexGenerator.GenerateExpression(elementNumber);
parsedRegex = new Regex(regex);
//Pick which string will be the correct one
correctID = randomGen.Next(4);
for (int i = 0; i < 4; i++)
{
//Generate a random string that matches the expression
string matchString = parsedRegex.RandomString();
//If this string is not supposed to be correct, make it invalid
if (i == correctID) options[i] = matchString;
else options[i] = GenerateInvalidString(matchString);
//This way, each string will be generated from a different string
//that matches the expression, hence, the 4 strings won't look similar
}
}
/// <summary>
/// Shows a hint to this question to the user
/// </summary>
public void DisplayHint()
{
//Bail out if the hint has already been displayed for this question
if (!hintAvailable) return;
//Hint no longer available
hintAvailable = false;
//Get a random answer that matches this regex
Regex parsedExp = new Regex(questionRegex);
char[] randomAnswer = parsedExp.RandomString().ToCharArray();
//Replace some characters in it with underscores
for (int i = 0; i < randomAnswer.Length; i++)
{
if (randGen.Next() % 3 == 0) randomAnswer[i] = '_';
}
//Display the hint
txtHint.Text = "Hint: " + new string(randomAnswer);
txtHint.Show();
}
