Adv2015/D15.2/Program.cs

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

namespace D15._2
{
    public class Recipe
    {
        public Ingredient I;
        public (Recipe R, int Qt) R;
    }

    public class Ingredient
    {
        public string Name;
        public int Capacity;
        public int Durability;
        public int Flavor;
        public int Texture;
        public int Calories;
    }

    class Program
    {
        static int EvaluateRecipe((Recipe ingredient, int qt) recipe)
        {
            int capacity = 0, durability = 0, flavor = 0, texture = 0, calories = 0;

            while (recipe.ingredient != null)
            {
                (Recipe nrecipe, int qt) = recipe;
                var i = nrecipe.I;

                capacity += i.Capacity * qt;
                durability += i.Durability * qt;
                flavor += i.Flavor * qt;
                texture += i.Texture * qt;
                calories += i.Calories * qt;

                recipe = nrecipe.R;
            }

            if (calories != 500) return 0;
            return Math.Max(capacity, 0) * Math.Max(durability, 0) * Math.Max(flavor, 0) * Math.Max(texture, 0);
        }

        static int TestRecipes((Recipe ingredient, int qt) recipe, List<Ingredient> ingredients, int i = 0, int total = 0)
        {
            var ingr = ingredients[i];
            if (i == ingredients.Count - 1)
            {
                recipe = (new Recipe { R = recipe, I = ingr }, 100 - total);
                return EvaluateRecipe(recipe);
            }

            int bestRecipe = 0;
            for (int qt = 0; qt <= 100 - total; ++qt)
            {
                var result = TestRecipes((new Recipe { R = recipe, I = ingr }, qt), ingredients, i + 1, total + qt);
                if (result > bestRecipe) bestRecipe = result;
            }

            return bestRecipe;
        }

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

            var ingredients = new List<Ingredient>();

            ParseFile(args[0], ingredients);

            int bestRecipe = TestRecipes((null, 0), ingredients);

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

        private static void ParseFile(string f, List<Ingredient> ingredients)
        {
            var regex = new Regex(@"(?<n>\w+): capacity (?<c>-?\d+), durability (?<d>-?\d+), flavor (?<f>-?\d+), texture (?<t>-?\d+), calories (?<cs>-?\d+)");
            using (var file = File.OpenText(f))
            {
                while (true)
                {
                    var line = file.ReadLine();
                    if (line == null) break;
                    var result = regex.Match(line);

                    var i = new Ingredient();

                    i.Name = result.Groups["n"].Value;
                    i.Capacity = int.Parse(result.Groups["c"].Value);
                    i.Durability = int.Parse(result.Groups["d"].Value);
                    i.Flavor = int.Parse(result.Groups["f"].Value);
                    i.Texture = int.Parse(result.Groups["t"].Value);
                    i.Calories = int.Parse(result.Groups["cs"].Value);

                    ingredients.Add(i);
                }
            }
        }
    }
}