AdventOfCode/AdventOfCode.Solutions/2023/Day 03/Day03.cs

using AdventOfCode.Core;
using System.Text.RegularExpressions;
using static System.Runtime.InteropServices.JavaScript.JSType;

namespace AdventOfCode.Solutions._2023
{
    public partial class Day03(InputReader reader) : IChallange
    {
        private InputReader _inputReader = reader;

        private class PartNumber
        {
            public int X { get; set; }

            public int Y { get; set; }

            public string Section { get; set; } = string.Empty;

            public int Length => Section.Length;

            public bool IsDigit() => Section.Length > 1;

            public bool IsPartSymbol() => !IsDigit();

            public override string ToString()
            {
                return $"[{Y},{X}] {Section}";
            }
        }

        public async Task<string> GetSolutionPart1()
        {
            List<PartNumber> parts = [];
            int row = 0;
            int total = 0;
            await foreach (string line in _inputReader.ReadAsStringLine())
            {
                MatchCollection matchCollection = FindPartItems().Matches(line);
                parts.AddRange(matchCollection.Select(match => new PartNumber { X = match.Index, Y = row, Section = match.Value }));
                row++;
            }

            List<PartNumber> numbers = parts.Where(p => p.IsDigit()).ToList();
            List<PartNumber> symbols = parts.Where(p => p.IsPartSymbol()).ToList();

            var intersected = numbers.Where(number => GetSection(symbols, number.X - 1, number.Y - 1, number.X + number.Length, number.Y + 1).Any()).ToList();

            total = numbers.Where(number => GetSection(symbols, number.X - 1, number.Y - 1, number.X + number.Length, number.Y + 1).Any()).Sum(number => int.Parse(number.Section));

            //Grid<Node> grid = await _inputReader.ReadToGrid<Node>();
            //int row = 0;
            //
            //await foreach(string line in _inputReader.ReadAsStringLine())
            //{
            //    MatchCollection matchCollection = FindDigits().Matches(line);
            //    
            //    foreach (Match match in matchCollection.Cast<Match>())
            //    {
            //        var section = grid.GetSection(match.Index - 1, row - 1, match.Index + match.Length, row + 1).ToList();
            //        bool isPartNumber = section.Any(n => !(n.Char == '.' || (n.Char >= '0' && n.Char <= '9')));
            //        if (isPartNumber) {
            //            total += int.Parse(match.Value);
            //        }
            //    }
            //
            //    row++;
            //}

            return total.ToString();
        }

        public async Task<string> GetSolutionPart2()
        {
            List<PartNumber> parts = [];
            int row = 0;
            int total = 0;
            await foreach (string line in _inputReader.ReadAsStringLine())
            {
                MatchCollection matchCollection = FindPartItems().Matches(line);
                parts.AddRange(matchCollection.Select(match => new PartNumber { X = match.Index, Y = row, Section = match.Value }));
                row++;
            }

            List<PartNumber> numbers = parts.Where(p => p.IsDigit()).ToList();
            List<PartNumber> gears = parts.Where(p => p.IsPartSymbol() && p.Section == "*").ToList();

            foreach (PartNumber gear in gears)
            {
                // check if there are 2 numbers around
                List<PartNumber> ratios = GetSection(numbers, gear).ToList();

                if (ratios.Count != 2)
                    continue;

                int totalRatio = int.Parse(ratios[0].Section) * int.Parse(ratios[1].Section);

                total += totalRatio;
            }

            return total.ToString();
        }

        private IEnumerable<PartNumber> GetSection(List<PartNumber> toSearch, int fromX, int fromY, int toX, int toY)
        {
            return toSearch.Where(node => node.X >= fromX && node.X + node.Length <= toX && node.Y >= fromY && node.Y <= toY);
        }

        private IEnumerable<PartNumber> GetSection(List<PartNumber> toSearch, PartNumber source)
        {
            return toSearch.Where(target => 
                target.X >= source.X - 1 && 
                target.X + target.Length <= source.X && 
                target.Y >= source.Y - 1 && 
                target.Y <= source.Y + 1);
        }

        [GeneratedRegex("(\\d+)", RegexOptions.Compiled)]
        private static partial Regex FindDigits();

        [GeneratedRegex("(\\d+)|([^.])", RegexOptions.Compiled)]
        private static partial Regex FindPartItems();
    }
}