Adv2018/D25.1/Program.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace D25._1
{
    public class Star
    {
        public List<Star> Connections = new List<Star>();

        public int[] Coords;

        public override bool Equals(object obj)
        {
            var star = obj as Star;
            return star != null && EqualityComparer<int[]>.Default.Equals(Coords, star.Coords);
        }

        public override int GetHashCode()
        {
            return Coords.GetHashCode();
        }
    }

    class Program
    {
        static public int Manhattan(int[] a, int[] b)
        {
            int man = 0;
            for (var i = 0; i < a.Length; ++i)
                man += Math.Abs(a[i] - b[i]);
            return man;
        }

        static void Main(string[] args)
        {
            if (args.Length < 1) return;
            if (File.Exists(args[0]) == false) return;

            List<Star> all = new List<Star>();

            var file = File.OpenText(args[0]);

            do
            {
                var line = file.ReadLine();
                if (line == null) break;

                var coord = line.Split(",").Select(v => int.Parse(v)).ToArray();

                var star = new Star()
                {
                    Coords = coord
                };

                foreach (var a in all)
                {
                    if (Manhattan(a.Coords, star.Coords) > 3) continue;
                    a.Connections.Add(star);
                    star.Connections.Add(a);
                }

                all.Add(star);

            } while (true);

            file.Close();

            HashSet<Star> visited = new HashSet<Star>();
            Queue<Star> queue = new Queue<Star>();

            int constellations = 0;

            while (true)
            {
                var first = all.Where(a => visited.Contains(a) == false).FirstOrDefault();
                if (first == null) break;

                constellations++;
                queue.Enqueue(first);

                while (queue.Count > 0)
                {
                    var s = queue.Dequeue();

                    visited.Add(s);
                    foreach (var c in s.Connections)
                    {
                        if (visited.Contains(c)) continue;
                        queue.Enqueue(c);
                    }
                }

            }

            Console.WriteLine($"The answer is : {constellations}");
        }
    }
}