AdventOfCode2022/Handlers/Day03.cs

namespace AdventOfCode2022.Handlers
{
    public class Day03
    {
        string[] letters = new string[] {};
        string[] rucksack = new string[] {};
        public Day03()
        {
            rucksack = File.ReadAllText(@"./days/03/input").Trim().Split("\n");

            // a-z
            for (var i = 97; i <= 122; i++)
            {
                letters = letters.Append(((char)i).ToString()).ToArray();
            }

            // A-Z
            for (var i = 65; i <= 90; i++)
            {
                letters = letters.Append(((char)i).ToString()).ToArray();
            }
        }

        public int GetLetterPriority(string letter)
        {
            return Array.IndexOf(letters, letter) + 1;
        }

        public void PartA()
        {
            var sum = 0;
            foreach (var line in rucksack)
            {
                var lineLength = line.Length;
                var halfPoint = lineLength / 2;
                var partOne = line.Substring(0, halfPoint);
                var partTwo = line.Substring(halfPoint);
                
                var firstParts = partOne.ToArray();
                var secondParts = partTwo.ToArray();
                var diffLetter = "";

                foreach (var letter in firstParts)
                {
                    if (secondParts.Contains(letter))
                    {
                        diffLetter = letter.ToString();
                        break;
                    }
                }

                if (diffLetter == "")
                {
                    Console.WriteLine("No diff letter found");
                }

                sum += GetLetterPriority(diffLetter);
            }

            Console.WriteLine($"Part A: {sum}");
        }

        public void PartB()
        {
            var groups = rucksack.Chunk(3);
            var sum = 0;
            foreach (var group in groups)
            {
                var firstSackLetters = group[0];
                var commonLetter = "";
                foreach (var ch in firstSackLetters)
                {
                    var letter = Convert.ToString(ch);
                    var exists = group.All(x => x.Contains(letter));
                    if (exists)
                    {
                        commonLetter = letter;
                        break;
                    }
                }

                if (commonLetter == "")
                {
                    Console.WriteLine("No common letter found");
                }

                sum += GetLetterPriority(commonLetter);
            }

            Console.WriteLine($"Part B: {sum}");
        }
    }
}