Adv2015/D09.1/Program.cs

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

namespace D09._1
{
    public class VisitedList
    {
        public Place Visited;
        private VisitedList Next;
        public VisitedList(VisitedList list) => Next = list;
        public bool Contains(Place place)
        {
            if (Visited?.Equals(place) ?? false) return true;
            return Next?.Contains(place) ?? false;
        }
        public int Count() => 1 + Next?.Count() ?? 1;
    }

    public class Place
    {
        public string Name { get; }

        public Place(string name) => Name = name;

        public HashSet<(int distance, Place neighbor)> Neighbors = new HashSet<(int distance, Place neighbor)>();

        public override bool Equals(object obj)
        {
            var place = obj as Place;
            return place != null &&
                   Name == place.Name;
        }

        public override int GetHashCode()
        {
            return HashCode.Combine(Name);
        }
    }

    class Program
    {
        static (int best, int worst) TestTravelRoutes(Dictionary<string, Place> places, Place start = null, VisitedList visited = null, int traveled = 0)
        {
            if (visited?.Count() == places.Count)
                return (traveled, traveled);

            int best = -1, worst = -1;
            foreach ((int distance, Place neighbor) in start?.Neighbors ?? places.Values.Select(v => (0, v)))
            {
                if (visited?.Contains(neighbor) ?? false) continue;

                (int b, int w) = TestTravelRoutes(places, neighbor, new VisitedList(visited) { Visited = start }, traveled + distance);

                if (best == -1 || b < best) best = b;
                if (w > worst) worst = w;
            }

            return (best, worst);
        }

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

            Dictionary<string, Place> places = new Dictionary<string, Place>();

            ParseFile(args, places);

            (int best, int worst) = TestTravelRoutes(places);

            Console.WriteLine($"The best distance is : {best}");
            Console.WriteLine($"The worst distance is : {worst}");
        }

        private static void ParseFile(string[] args, Dictionary<string, Place> places)
        {
            using (var file = File.OpenText(args[0]))
            {
                while (true)
                {
                    var line = file.ReadLine();
                    if (line == null) break;

                    var spl = line.Split(" = ");
                    var ft = spl[0].Split(" to ");

                    string from = ft[0], to = ft[1];
                    int distance = int.Parse(spl[1]);

                    places.TryGetValue(from, out var placeFrom);
                    places.TryGetValue(to, out var placeTo);

                    if (placeFrom == null)
                    {
                        placeFrom = new Place(from);
                        places.Add(from, placeFrom);
                    }
                    if (placeTo == null)
                    {
                        placeTo = new Place(to);
                        places.Add(to, placeTo);
                    }

                    placeFrom.Neighbors.Add((distance, placeTo));
                    placeTo.Neighbors.Add((distance, placeFrom));
                }
            }
        }
    }
}