AdventOfCode2022/Handlers/Day02.cs

namespace AdventOfCode2022.Handlers
{
    public class Day02
    {
        public enum GameResult
        {
            Loss = 0,
            Draw = 3,
            Win = 6
        }

        public enum Choice
        {
            Rock = 1,
            Paper = 2,
            Scissors = 3
        }

        string[] rounds;

        public Day02()
        {
            rounds = System.IO.File.ReadAllText(@"./days/02/input").Trim().Split("\n");
        }

        private Choice ParseChoice(string input)
        {
            switch (input)
            {
                case "A":
                case "X":
                    return Choice.Rock;

                case "B":
                case "Y":
                    return Choice.Paper;

                case "C":
                case "Z":
                    return Choice.Scissors;

                default:
                    throw new Exception($"Invalid choice: {input}");
            }
        }

        private GameResult PartAGameResult(Choice opponent, Choice you)
        {
            if (you == opponent)
            {
                return GameResult.Draw;
            }

            if (you == Choice.Rock && opponent == Choice.Scissors)
            {
                return GameResult.Win;
            }

            if (you == Choice.Paper && opponent == Choice.Rock)
            {
                return GameResult.Win;
            }

            if (you == Choice.Scissors && opponent == Choice.Paper)
            {
                return GameResult.Win;
            }

            return GameResult.Loss;
        }

        private GameResult PartBGameResult(string input)
        {
            switch (input)
            {
                case "X":
                    return GameResult.Loss;

                case "Y":
                    return GameResult.Draw;

                case "Z":
                    return GameResult.Win;

                default:
                    throw new Exception($"Invalid choice: {input}");
            }
        }

        public void PartA()
        {
            var totalPoints = 0;

            foreach (var line in rounds)
            {
                var parts = line.Split(" ");
                var opponent = ParseChoice(parts[0]);
                var you = ParseChoice(parts[1]);
                var result = PartAGameResult(opponent, you);

                var points = (int)you + (int)result;
                totalPoints += points;
            }

            Console.WriteLine($"Part A - Total points: {totalPoints}");
        }

        public Choice PartBChoiceFromResult(GameResult result, Choice opponent)
        {
            if (result.Equals(GameResult.Win))
            {
                switch (opponent)
                {
                    case Choice.Rock:
                        return Choice.Paper;

                    case Choice.Paper:
                        return Choice.Scissors;

                    case Choice.Scissors:
                        return Choice.Rock;
                }
            }

            if (result.Equals(GameResult.Loss))
            {
                switch (opponent)
                {
                    case Choice.Rock:
                        return Choice.Scissors;

                    case Choice.Paper:
                        return Choice.Rock;

                    case Choice.Scissors:
                        return Choice.Paper;
                }
            }

            // Draw
            return opponent;
        }

        public void PartB()
        {
            var totalPoints = 0;

            foreach (var line in rounds)
            {
                var parts = line.Split(" ");
                var opponent = ParseChoice(parts[0]);
                var result = PartBGameResult(parts[1]);

                Choice? you = PartBChoiceFromResult(result, opponent);

                totalPoints += (int)you + (int)result;
            }

            Console.WriteLine($"Part B - Total points: {totalPoints}");
        }
    }
}