public void Execute()
{
Console.WriteLine("");
Console.WriteLine("--- Day 9: Encoding Error ---");
Console.WriteLine("---------------------------------------------");
string[] input = File.ReadAllLines(Directory.GetCurrentDirectory() + "\\Files\\Day9-Input.txt");
ResultXMASEncrypted firstInvalidNumber = GetFirstInvalid(input, 25);
Console.WriteLine("First number that is not a sum: {0}", firstInvalidNumber.firstInvalidNumber);
double sum = GetWeakness(input, firstInvalidNumber);
Console.WriteLine("The encryption weakness is: {0}", sum);
}
private ResultXMASEncrypted GetFirstInvalid(string[] input, int numberOfElements)
{
ResultXMASEncrypted firstInvalidNumber = new ResultXMASEncrypted();
try
{
for (int i = numberOfElements; i < input.Length; i++)
{
int.TryParse(input[i], out int currentNumber);
bool isSum = false;
int firstOperandPosition = i - 1;
while (firstOperandPosition > i - numberOfElements)
{
int.TryParse(input[firstOperandPosition], out int firstOperand);
int secondOperandPosition = firstOperandPosition - 1;
while (secondOperandPosition >= i - numberOfElements)
{
int.TryParse(input[secondOperandPosition], out int secondOperand);
if ((firstOperand + secondOperand) == currentNumber)
{
isSum = true;
break;
}
else
{
secondOperandPosition--;
}
}
if (isSum)
{
break;
}
else
{
firstOperandPosition--;
}
}
if (!isSum)
{
firstInvalidNumber.firstInvalidNumber = currentNumber.ToString();
firstInvalidNumber.firstInvalidPosition = i;
break;
}
}
}
catch (Exception ex) { Debug.WriteLine(ex.Message); }
return(firstInvalidNumber);
}
private double GetWeakness(string[] input, ResultXMASEncrypted firstInvalidNumber)
{
double sum = 0;
try
{
List <double> operands = new List <double>();
double.TryParse(firstInvalidNumber.firstInvalidNumber, out double firstInvalid);
for (int i = firstInvalidNumber.firstInvalidPosition - 1; i >= 0; i--)
{
operands = new List <double>();
double.TryParse(input[i], out double currentSum);
operands.Add(currentSum);
int currentOperand = i - 1;
while (currentSum < firstInvalid)
{
double.TryParse(input[currentOperand], out double currentOperandValue);
currentSum += currentOperandValue;
operands.Add(currentOperandValue);
currentOperand--;
}
if (currentSum == firstInvalid)
{
break;
}
}
if (operands.Count >= 2)
{
operands.Sort();
sum = operands[0] + operands[operands.Count - 1];
}
}
catch (Exception ex) { Debug.WriteLine(ex.Message); }
return(sum);
}