/// <summary>
/// https://projecteuler.net/problem=59
/// </summary>
/// <param name="arguments"></param>
/// <returns></returns>
public static Result XorDecryption(Problem arguments)
{
const char FirstChar = 'a';
const char LastChar = 'z';
var sum = 0;
var key = string.Empty;
var text = string.Empty;
var cvsinfo = arguments.Sequence.Split('|');
var fileName = cvsinfo[0];
var delimiter = Convert.ToChar(cvsinfo[1]);
var qualifier = Convert.ToChar(cvsinfo[2]);
var cyphers = UtilityFile.ReadCsvToArray(fileName, delimiter, qualifier);
var ascii = cyphers.Select(X => Convert.ToInt32(X)).ToArray();
var allPossiblePasswords = (from a in FirstChar.To(LastChar)
from b in FirstChar.To(LastChar)
from c in FirstChar.To(LastChar)
select new[] { Convert.ToInt32(a), Convert.ToInt32(b), Convert.ToInt32(c) }).ToArray();
foreach (var password in allPossiblePasswords)
{
var decrypted = UtilityMath.Encrypt(ascii, password);
text = new string(decrypted.Select(x => Convert.ToChar(x)).ToArray());
if (text.Contains(" the ")) //perform simple check: if Text contains single word 'the' it is in english
{
key = new string(password.Select(x => Convert.ToChar(x)).ToArray());
break;
}
}
sum = text.Aggregate(0, (runningTotal, next) => runningTotal += next);
var answer = sum.ToString();
var message = string.Format("The sum of the ASCII values in the original English text is {0}.", answer);
if (Answers[arguments.Id] != answer)
{
message += string.Format(" => INCORRECT ({0})", Answers[arguments.Id]);
}
var r = new Result(arguments.Id, message)
{
Answer = answer
};
return(r);
}