AdventOfCodeDay9-Main.cs

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

namespace AdventOfCodeDay9
{
	class MainClass
	{
		public static void Main (string[] args)
		{
			var sr = new StreamReader ("../../input1.txt"); // select part one or two here.
			string line;

			var regex = new Regex ("^(?<City1>.*?) to (?<City2>.*?) = (?<Distance>.*?)$");

			var distances = new Dictionary<string, int> ();
			var cities = new List<string> ();
			 
			while ((line = sr.ReadLine ()) != null) {
				var m = regex.Match (line);
				if (m.Success) {
					var city1 = m.Groups ["City1"].Value;
					var city2 = m.Groups ["City2"].Value;
					cities.Add (city1);
					cities.Add (city2);
					var distance = int.Parse (m.Groups ["Distance"].Value);
					distances.Add ($"{city1}-{city2}", distance);
				} else {
					throw new Exception ("Oh Noes!");
				}
			}

			Console.WriteLine (distances.Count);

			cities = cities.Distinct ().ToList ();
			cities.ForEach (Console.WriteLine);


			var allPaths = cities.Permute ();

			var shortest = DistanceForPath (distances, cities);
			var longest = shortest;

			foreach (var p in allPaths) {
				var dist = DistanceForPath (distances, p.ToList ());
				Console.WriteLine (dist + ": " + string.Join ("-", p));
				shortest = Math.Min (dist, shortest);
				longest = Math.Max (dist, longest);
			}

			Console.WriteLine ($"Shortest {shortest}");
			Console.WriteLine ($"Longest {longest}");
		}

		private static int DistanceForPath (Dictionary<string, int> distances, List<string> path)
		{
			int dist = 0;
			for (int i = 0; i < path.Count () - 1; i++) {
				var key = $"{path[i]}-{path[i+1]}";
				if (!distances.ContainsKey (key)) {
					key = $"{path[i+1]}-{path[i]}";
				}
				dist += distances [key];
			}
			return dist;
		}
	}
}