AdventOfCode/Days/Day13.cs

using System.Collections.Frozen;
using System.Numerics;
using System.Text;
using Spectre.Console;

namespace AdventOfCode.Days;

public class Day13 : Day
{
    public override int Number => 13;
    public override string Name => "Claw Contraption";

    private const int MaxButtonPress = 100;
    private const int ButtonACost = 3;
    private const int ButtonBCost = 1;

    public override void RunPart1(bool display = true)
    {
        var lines = Input.AsSpan().EnumerateLines();

        var minimumTokensToWin = 0;

        while (lines.MoveNext())
        {
            var (aX, aY, bX, bY, goalX, goalY) = ParseMachine(ref lines);

            for (var i = MaxButtonPress; i >= 0; i--)
            {
                var xOffset = bX * i;

                if (xOffset > goalX)
                {
                    continue;
                }

                if ((goalX - xOffset) % aX != 0)
                {
                    continue;
                }

                var timesAPressed = (goalX - xOffset) / aX;

                if (bY * i + aY * timesAPressed != goalY)
                {
                    continue;
                }

                minimumTokensToWin += i * ButtonBCost + timesAPressed * ButtonACost;

                break;
            }
        }

        if (display)
        {
            AnsiConsole.MarkupLine($"[green]Minimum tokens to win all prizes: [yellow]{minimumTokensToWin}[/][/]");
        }
    }

    public override void RunPart2(bool display = true)
    {

    }

    private (int aX, int aY, int bX, int bY, int goalX, int goalY) ParseMachine(ref SpanLineEnumerator lines)
    {
        var lineA = lines.Current;
        lines.MoveNext();

        var lineB = lines.Current;
        lines.MoveNext();

        var lineGoal = lines.Current;
        lines.MoveNext();

        return (
            int.Parse(lineA[(lineA.IndexOf('+') + 1)..lineA.IndexOf(',')]),
            int.Parse(lineA[(lineA.LastIndexOf('+') + 1)..]),

            int.Parse(lineB[(lineB.IndexOf('+') + 1)..lineB.IndexOf(',')]),
            int.Parse(lineB[(lineB.LastIndexOf('+') + 1)..]),

            int.Parse(lineGoal[(lineGoal.IndexOf('=') + 1)..lineGoal.IndexOf(',')]),
            int.Parse(lineGoal[(lineGoal.LastIndexOf('=') + 1)..])
        );
    }
}