AdventOfCode/AdventOfCode.Solutions/2024/Day 03/Day03.cs

using AdventOfCode.Core.Shared.IO;
using System.Text.RegularExpressions;

namespace AdventOfCode.Solutions._2024
{
    public partial class Day03 : IChallange
    {
        public int Year => 2024;
        public int Day => 3;

        private readonly IInputReader _inputReader;

        public Day03(IInputReader inputReader)
        {
            _inputReader = inputReader;
            _inputReader.SetInput(this);
        }

        //161
        //159833790
        public async Task<string> GetSolutionPart1()
        {
            string input = await _inputReader.ReadAsString();
            return ProcessInstructions(input).ToString();
        }

        //48
        //89349241
        public async Task<string> GetSolutionPart2()
        {
            string input = await _inputReader.ReadAsString();
            return ProcessInstructions(input, true).ToString();
        }

        private int ProcessInstructions(string instructions, bool extraInstructoins = false)
        {
            bool calc = true;
            int total = 0;

            MatchCollection collection = MulMatcher().Matches(instructions);

            foreach (string matchedText in collection.Select(m => m.Value))
            {
                // mul(5,5) is atleast 8 char so any match smaller than 8 is an instruction
                if (matchedText.Length <= 7)
                {
                    if (extraInstructoins)
                    {
                        //do() is only 4 chars, don't() is 7
                        calc = matchedText.Length == 4; 
                    }
                    
                    continue;
                }

                if (calc)
                {
                    total += GetMultiplications(matchedText);
                }
            }

            return total;
        }

        private int GetMultiplications(string match)
        {
            MatchCollection collection = NumberMatcher().Matches(match);
            int[] numbers = collection.Select(m => m.Value).Select(int.Parse).ToArray();
            return numbers[0] * numbers[1];
        }

        [GeneratedRegex(@"(mul\(\d{1,3},\d{1,3}\))|(do\(\))|(don't\(\))")]
        private static partial Regex MulMatcher();

        [GeneratedRegex(@"(\d{1,3})")]
        private static partial Regex NumberMatcher();
    }
}