Adv2018/D10.2/Program.cs

using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

namespace D10._2
{
    class Map : List<(int x, int y, int vx, int vy)> { }

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

            var r = new Regex(@"position=<\s*(?<posx>-?\d+),\s*(?<posy>-?\d+)> velocity=<\s*(?<vx>-?\d+),\s*(?<vy>-?\d+)>");

            var map = new Map();

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

                var result = r.Match(line);

                map.Add((
                    int.Parse(result.Groups["posx"].Value),
                    int.Parse(result.Groups["posy"].Value),
                    int.Parse(result.Groups["vx"].Value),
                    int.Parse(result.Groups["vy"].Value)
                ));

            } while (true);

            int tt = 0;
            do
            {
                for (var i = 0; i < map.Count; ++i)
                {
                    var star = map[i];

                    star.x += star.vx;
                    star.y += star.vy;

                    map[i] = star;
                }

                tt++;
            } while (isOk(map) == false);

            Console.WriteLine($"Answer is : {tt}s");
        }

        static bool isOk(Map map)
        {
            for (var i = 0; i < map.Count; ++i)
                if (isIsolated(map, i)) return false;
            return true;
        }

        static bool isIsolated(Map map, int current)
        {
            var currentStar = map[current];
            foreach (var star in map)
            {
                if (star.x == currentStar.x && star.y == currentStar.y)
                    continue;

                if (star.x == currentStar.x && (star.y == currentStar.y + 1 || star.y == currentStar.y - 1))
                    return false;
                if (star.y == currentStar.y && (star.x == currentStar.x + 1 || star.x == currentStar.x - 1))
                    return false;

                if ((star.x == currentStar.x + 1 || star.x == currentStar.x - 1) && (star.y == currentStar.y + 1 || star.y == currentStar.y - 1))
                    return false;
                if ((star.y == currentStar.y + 1 || star.y == currentStar.y - 1) && (star.x == currentStar.x + 1 || star.x == currentStar.x - 1))
                    return false;
            }

            return true;
        }
    }
}