AdventOfCode/AdventOfCode.Solutions/2023/Day 07/Day07.cs

using AdventOfCode.Core;

namespace AdventOfCode.Solutions._2023
{
    public class Day07(InputReader reader) : IChallange
    {
        private readonly InputReader _inputReader = reader;

        private static readonly List<char> CardValues = ['1', '2', '3', '4', '5', '6', '7', '8', '9', 'T', 'J', 'Q', 'K', 'A'];
        private static readonly List<char> CardValuesJoker = ['J', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'T', 'Q', 'K', 'A'];
        private enum SetRanks { High, OnePair, TwoPair, ThreeKind, FullHouse, FourKind, FiveKind }

        public async Task<string> GetSolutionPart1()
        {
            return (await _inputReader.ReadAsArrayString())
                .Select(l => new Hand(l))
                .Order()
                .Select((h, i) => h.Bid * (i + 1))
                .Sum()
                .ToString();
        }

        public async Task<string> GetSolutionPart2()
        {
            return (await _inputReader.ReadAsArrayString())
                .Select(l => new Hand(l, true))
                .Order()
                .Select((h, i) => h.Bid * (i + 1))
                .Sum()
                .ToString();
        }

        private record Hand : IComparable<Hand> 
        { 
            public int Bid { get; set; }
            public SetRanks Rank { get; set; }
            public string Source { get; set; }
            public string JokerSource { get; set; } = string.Empty;
            public List<char> CharCompairList => string.IsNullOrEmpty(JokerSource) ? CardValues : CardValuesJoker;

            public Hand(string line, bool jokerMode = false)
            {
                string[] splitted = line.Split(' ');
                Source = splitted[0];
                Bid = int.Parse(splitted[1]);

                string finalTestLine = Source;
                if (jokerMode)
                {
                    JokerSource = Source;
                    if (finalTestLine.Contains('J') && finalTestLine.Any(c => c != 'J'))
                    {
                        // fun time
                        char toReplace = finalTestLine.Where(c => c != 'J').GroupBy(c => c).OrderByDescending(g => g.Count()).First().Key;
                        finalTestLine = finalTestLine.Replace('J', toReplace);
                        JokerSource = finalTestLine;
                    }
                }

                var grouped = finalTestLine.GroupBy(c => c).OrderByDescending(g => g.Count());
                
                switch(grouped.Count())
                {
                    case 1:
                        Rank = SetRanks.FiveKind; 
                        break;
                    case 4:
                        Rank = SetRanks.OnePair;
                        break;
                    case 5:
                        Rank = SetRanks.High;
                        break;
                    case 3:
                        if (grouped.Skip(1).First().Count() == 2)
                            Rank = SetRanks.TwoPair;
                        else
                            Rank = SetRanks.ThreeKind;
                        break;
                    case 2:
                        if (grouped.First().Count() == 4)
                            Rank = SetRanks.FourKind;
                        else
                            Rank = SetRanks.FullHouse;
                        break;
                }
            }

            public override string ToString()
            {
                return $"{JokerSource} [{Source}] {Rank} {Bid}";
            }

            public int CompareTo(Hand? other)
            {
                if (other == null)
                    return 1;

                if (this.Rank == other.Rank && this.Source == other.Source) 
                    return 0;

                if (this.Rank > other.Rank) 
                    return 1;
                if (this.Rank < other.Rank) 
                    return -1;

                for (int i = 0; i < Source.Length; i++)
                {
                    if (this.Source[i] == other.Source[i]) 
                        continue;
                    if (CharCompairList.IndexOf(this.Source[i]) > CharCompairList.IndexOf(other.Source[i]))
                        return 1;
                    if (CharCompairList.IndexOf(this.Source[i]) < CharCompairList.IndexOf(other.Source[i]))
                        return -1;
                }

                return 0;
            }
        }

        
    }
}