AdventOfCodeDay13.cs

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

namespace AdventOfCodeDay13
{
	class Program
	{
		static void Main(string[] args)
		{
			StreamReader ss = new StreamReader("../../input1.txt");

			string line;
			var input = new List<string>();
			while ((line = ss.ReadLine()) != null)
			{
				input.Add(line);
			}

			var regex = new Regex("^(?<Name1>.*) would (?<Sign>.*) (?<Value>[0-9]+) happiness units by sitting next to (?<Name2>.*).$");

			var persons = new List<Person>();
			var happynessChangeDictionary = new Dictionary<string, int>();

			foreach (var c in input)
			{
				var m = regex.Matches(c)[0];

				var name1 = m.Groups["Name1"].Value;
				var name2 = m.Groups["Name2"].Value;
				var sign = m.Groups["Sign"].Value;
				var value = int.Parse(m.Groups["Value"].Value);

				Console.WriteLine($"{name1}, {name2}, {sign}, {value}");

				if (persons.All(a => a.Name != name1))
				{
					persons.Add(new Person { Name = name1, HappynessChangeLeft = 0, HappynessChangeRight = 0 });
				}

				happynessChangeDictionary.Add($"{name1}-{name2}", (sign == "lose" ? -1 : 1) * value);
			}

			var arrangements = persons.Permute().ToList();

			var maxHappyness = 0;

			foreach (var arrangement in arrangements)
			{
				var arrangementList = arrangement.ToList();
				var cnt = arrangementList.Count();

				for (var i = 0; i < cnt; i++)
				{
					var leftIndex = Mod(i - 1, cnt);
					var rightIndex = Mod(i + 1, cnt);

					var self = arrangementList[i];
					var left = arrangementList[leftIndex];
					var right = arrangementList[rightIndex];

					var leftKey = $"{self.Name}-{left.Name}";
					var rightKey = $"{self.Name}-{right.Name}";

					self.HappynessChangeLeft = happynessChangeDictionary[leftKey];
					self.HappynessChangeRight = happynessChangeDictionary[rightKey];
				}

				maxHappyness = Math.Max(maxHappyness, arrangementList.Sum(a => a.TotalHappynessChange));
			}
			 
			Console.WriteLine($"Optimal change: {maxHappyness}");

			Console.ReadLine();
		}

		public class Person
		{
			public string Name { get; set; }

			public int HappynessChangeLeft { get; set; }
			public int HappynessChangeRight { get; set; }

			public int TotalHappynessChange => HappynessChangeLeft + HappynessChangeRight;
		}

		public static int Mod(int x, int m)
		{
			return (x % m + m) % m;
		}
	}
}