AdventOfCode/2024/Day02CSharp/Program.cs

Day02Parsed exParsed = new Day02Parsed("example-input.txt");

Console.WriteLine("Example Part01: {0}", exParsed.GetSafeReportCount01());
Console.WriteLine("Example Part02: {0}", exParsed.GetSafeReportCount02());

Day02Parsed pzParsed = new Day02Parsed("puzzle-input.txt");

Console.WriteLine("Puzzle Part01: {0}", pzParsed.GetSafeReportCount01());
Console.WriteLine("Puzzle Part02: {0}", pzParsed.GetSafeReportCount02());

class Day02Parsed : AdventCommon.ParsedInput
{
    List<List<int>> Reports = new List<List<int>>();

    public Day02Parsed(string fileName) : base(fileName)
    {
        
    }

    public int GetSafeReportCount01()
    {
        int count = 0;

        for (int i = 0; i < Reports.Count; i++)
        {
            if (IsSafe(Reports[i]))
            {
                count++;
            }
        }

        return count;
    }

    public int GetSafeReportCount02()
    {
        int count = 0;

        for (int i = 0; i < Reports.Count; i++)
        {
            // First see if its safe outright
            if (IsSafe(Reports[i]))
            {
                count++;
            }
            else 
            {
                // Remove one start to end and check again
                for (int j = 0; j < Reports[i].Count; j++)
                {
                    List<int> newReport = new List<int>(Reports[i]);
                    newReport.RemoveAt(j);
                    if (IsSafe(newReport))
                    {
                        count++;
                        break;
                    }
                }
            }
        }

        return count;
    }

    public bool IsSafe(List<int> report)
    {
        bool isAscending = false;

        if ( report[0] < report[1] )
        {
            isAscending = true;
        }

        {
            int rightDiff = report[1] - report[0];

            if (Math.Abs(rightDiff) < 1 || Math.Abs(rightDiff) > 3)
            {
                return false;
            }
        }

        for (int i = 1; i < report.Count - 1; i++)
        {
            int leftDiff = report[i] - report[i - 1];
            int rightDiff = report[i + 1] - report[i];

            // if ascending and either difference is negative, not safe
            if (isAscending && (leftDiff < 0 || rightDiff < 0))
            {
                return false;
            }
            // if descending and either difference is positive, not safe
            else if (!isAscending && (rightDiff > 0 || leftDiff > 0))
            {
                return false;
            }

            if (Math.Abs(leftDiff) < 1 || Math.Abs(leftDiff) > 3)
            {
                return false;
            }

            if (Math.Abs(rightDiff) < 1 || Math.Abs(rightDiff) > 3)
            {
                return false;
            }
        }

        {
            int leftDiff = report[report.Count - 1] - report[report.Count - 2];
            if (isAscending && leftDiff < 0)
            {
                return false;
            }

            if (Math.Abs(leftDiff) < 1 || Math.Abs(leftDiff) > 3)
            {
                return false;
            }
        }

        return true;
    }


    public override bool ParseLine(string line, object? context = null)
    {
        List<int> levels = new List<int>();
        var split = line.Split(' ', StringSplitOptions.RemoveEmptyEntries);

        foreach (var level in split)
        {
            levels.Add(Int32.Parse(level));
        }

        Reports.Add(levels);

        return true;
    }
}