AdventOfCode/Days/Day1.cs

using Spectre.Console;

namespace AdventOfCode.Days;

public class Day1 : Day
{
    public override int Number => 1;
    public override string Name => "Secret Entrance";

    public override void RunPart1(bool display = true)
    {
        var password = 0;
        var dialPosition = 50;

        foreach (var line in Input.EnumerateLines())
        {
            var direction = line[0];
            var offset = int.Parse(line[1..]);

            var sign = direction is 'L'
                ? -1
                : +1;

            dialPosition = MathMod(dialPosition + (offset * sign), 100);

            if (dialPosition is 0)
            {
                password++;
            }
        }

        if (display)
        {
            AnsiConsole.MarkupLine($"[green]Safe password is: [yellow]{password}[/][/]");
        }
    }

    public override void RunPart2(bool display = true)
    {
        var password = 0;
        var dialPosition = 50;

        foreach (var line in Input.EnumerateLines())
        {
            var direction = line[0];
            var offset = int.Parse(line[1..]);

            var originalSign = Math.Sign(dialPosition);

            var sign = direction is 'L'
                ? -1
                : +1;

            dialPosition = dialPosition + (offset * sign);

            int clickCount;
            if (dialPosition is 0)
            {
                clickCount = 1;
            }
            else
            {
                clickCount = Math.Abs(dialPosition) / 100; // Number of times the dial passed by 0

                // If we did a loop around it counts as a "click" too
                if (originalSign != 0 && originalSign != Math.Sign(dialPosition))
                {
                    clickCount++;
                }
            }

            dialPosition = MathMod(dialPosition, 100);

            password += clickCount;
        }

        if (display)
        {
            AnsiConsole.MarkupLine($"[green]Safe password is: [yellow]{password}[/][/]");
        }
    }

    private static int MathMod(int left, int right)
    {
        return (Math.Abs(left * right) + left) % right;
    }
}