AdventOfCode/2023/Day03CSharp/Program.cs

using AdventCommon;
using System.ComponentModel.DataAnnotations;
using System.Numerics;

var p1exampleSln = Part01("example-input.txt");
var p1puzzleSln = Part01("puzzle-input.txt");

Console.WriteLine("Part01 Example Sum: " + p1exampleSln);
Console.WriteLine("Part01 Puzzle Sum: " + p1puzzleSln);

var p2exampleSln = Part02("example-input.txt");
var p2puzzleSln = Part02("puzzle-input.txt");

Console.WriteLine("Part02 Example Sum: " + p2exampleSln);
Console.WriteLine("Part02 Puzzle Sum: " + p2puzzleSln);

int Part01(string fileName)
{
    var input = new Day03Input(fileName);

    int sum = 0;
    foreach (var num in input.Numbers)
    {
        bool foundAdjacent = false;

        foreach (var s in input.Symbols)
        {
            if (Day03Input.Part.IsAdjacent(num, s))
            {
                foundAdjacent = true;
                break;
            }
        }

        if (foundAdjacent)
        {
            sum += num.Value;
        }
    }

    return sum;
}

int Part02(string fileName)
{
    var input = new Day03Input(fileName);

    int sum = 0;
    
    foreach (var symbol in input.Symbols.Where(x => x.S == '*'))
    {
        List<Day03Input.Number> adjacentNums = new List<Day03Input.Number>();

        foreach (var num in input.Numbers)
        {
            if (Day03Input.Part.IsAdjacent(num, symbol))
            {
                adjacentNums.Add(num);
            }
        }

        if (adjacentNums.Count == 2)
        {
            sum += adjacentNums[0].Value * adjacentNums[1].Value;
        }
    }

    return sum;
}

class Day03Input : PuzzleInput
{
    public abstract class Part
    {
        public Part(int x, int y, int length)
        {
            Coords = new Vector2(x, y);
            Length = length;
        }

        public Vector2 Coords { get; set; }
        public float X { get { return Coords.X; } }
        public float Y { get { return Coords.Y; } }
        public int Length { get; private set; }
        
        public static bool IsAdjacent(Part left, Part right)
        {
            for (int i = 0; i < left.Length; i++)
            {
                for (int j = 0; j < right.Length; j++)
                {
                    var l = new Vector2(left.X + i, left.Y);
                    var r = new Vector2(right.X + j, right.Y);

                    if (Vector2.Subtract(l, r).Length() < 2)
                        return true;
                }
            }

            return false;
        }
    }

    public class Number : Part
    {
        public Number(int x, int y, int value, int length) : base(x,y,length)
        {
            Value = value;
        }

        public int Value { get; private set; }
    }

    public class Symbol : Part
    {
        public Symbol(int x, int y, char s) : base(x,y,1)
        {
            S = s;
        }

        public char S { get; private set; }
    }

    public Day03Input(string fileName) : base(fileName)
    {
        for (int j = 0; j < Lines.Count; j++)
        {
            for (int i = 0; i < Lines[j].Length; i++)
            {
                if (Char.IsDigit(Lines[j][i]))
                {
                    string num = "";
                    for (int sub = i; sub < Lines[j].Length && Char.IsDigit(Lines[j][sub]); sub++)
                    {
                        num += Lines[j][sub];
                    }
                    int val = Int32.Parse(num);

                    var n = new Number(i, j, val, num.Length);
                    Numbers.Add(n);

                    // Skip remaining characters in the number
                    for (int upper = i + n.Length - 1; i < upper; i++) ;
                }
                else if (!Char.IsLetterOrDigit(Lines[j][i]) && Lines[j][i] != '.')
                {
                    var v = new Symbol(i, j, Lines[j][i]);
                    Symbols.Add(v);
                }
            }
        }
    }

    public List<Number> Numbers { get; set; } = new List<Number>();
    public List<Symbol> Symbols { get; set; } = new List<Symbol>();
}