AdventOfCode2025/AdventOfCode2026/Day1.cs

namespace AdventOfCode2026;

public sealed class Day1 : Solution
{
    private const int MaxArrow = 100;
    public override string SolvePart1()
    {
        var arrow = 50;
        var zeroCounter = 0;
        IEnumerable<string> lines = InputReader.ReadLines(1);
        foreach (var line in lines)
        {
            var number = int.Parse(line[1..]);
            arrow = line.First() switch
            {
                'L' => arrow - number,
                'R' => arrow + number,
                var _ => arrow
            };

            arrow = (arrow % MaxArrow + MaxArrow) % MaxArrow;
            if (arrow == 0)
            {
                zeroCounter++;
            }
        }

        return zeroCounter.ToString();
    }

    public override string SolvePart2()
    {
        var arrow = 50;
        var zeroCounter = 0;
        IEnumerable<string> lines = InputReader.ReadLines(1);

        foreach (var line in lines)
        {
            var number = int.Parse(line[1..]);
            zeroCounter += number / MaxArrow;
            var remainingNumber = number % MaxArrow;

            var end = line.First() switch
            {
                'L' => arrow - remainingNumber,
                'R' => arrow + remainingNumber,
                var _ => arrow
            };

            if (arrow != 0 && end is > MaxArrow or < 0)
            {
                zeroCounter++;
            }

            arrow = (end % MaxArrow + MaxArrow) % MaxArrow;
            if (arrow == 0)
            {
                zeroCounter++;
            }
        }

        return zeroCounter.ToString();
    }
}