AdventOfCode2021/AdventOfCode/2021/Day2.cs

namespace AdventOfCode._2021;

public class Day2
{
    public void Part1()
    {
        var input = File.ReadAllLines("2021/input/day2.txt");

        int h = 0;
        int d = 0;

        foreach (var s in input)
        {
            var split = s.Split(' ');
            (string direction, int units) = (split[0], int.Parse(split[1]));

            if (direction is "forward")
            {
                h += units;
            }
            else if (direction is "down")
            {
                d += units;
            }
            else
            {
                d -= units;
            }
        }

        Console.WriteLine(h * d);
    }

    public void Part2()
    {
        var input = File.ReadAllLines("2021/input/day2.txt");

        int h = 0;
        int d = 0;
        int aim = 0;

        foreach (var s in input)
        {
            var split = s.Split(' ');
            (char dir, int units) = (split[0][0], int.Parse(split[1]));

            switch (dir)
            {
                case 'f':
                    h += units;
                    d += aim * units;
                    break;

                case 'd':
                    aim += units;
                    break;

                case 'u':
                    aim -= units;
                    break;

                default:
                    throw new Exception(dir.ToString());
            }
        }

        Console.WriteLine(h * d); // first input isn't counted.
    }
}