Add solution for 2015 day 15

2015/README.md

@@ -16,7 +16,7 @@
 | ✓      | 12  | Ruby
 | ✓      | 13  | Ruby
 | ✓      | 14  | Ruby
-|        | 15  |
+| ✓      | 15  | Ruby
 |        | 16  |
 |        | 17  |
 |        | 18  |

2015/day-15/.ruby-version

@@ -0,0 +1 @@
+3.0.0

2015/day-15/inputs/puzzle.txt

@@ -0,0 +1,4 @@
+Sprinkles: capacity 2, durability 0, flavor -2, texture 0, calories 3
+Butterscotch: capacity 0, durability 5, flavor -3, texture 0, calories 3
+Chocolate: capacity 0, durability 0, flavor 5, texture -1, calories 8
+Candy: capacity 0, durability -1, flavor 0, texture 5, calories 8

2015/day-15/inputs/test.txt

@@ -0,0 +1,2 @@
+Butterscotch: capacity -1, durability -2, flavor 6, texture 3, calories 8
+Cinnamon: capacity 2, durability 3, flavor -2, texture -1, calories 3

2015/day-15/main.rb

@@ -0,0 +1,47 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require "pathname"
+
+Ingredient = Struct.new(:name, :capacity, :durability, :flavor, :texture, :calories, keyword_init: true)
+
+def parse_file(file)
+  file.each_line.map do |line|
+    line.split(": ") => [name, tail]
+    tail.split(", ").map(&:split).map { |(k, v)| [k.to_sym, v.to_i] }.to_h => properties
+    Ingredient.new(name: name, **properties)
+  end
+end
+
+# Not the most efficient solution, but it does its job
+def calculate_scores(ingredients)
+  size = ingredients.size
+
+  (1..(100 - size + 1)).to_a.repeated_permutation(size).select { |x| x.sum == 100 }.map do |perm|
+    total_score = %i[capacity durability flavor texture].reduce(1) do |total_score, property|
+      score = ingredients.each_with_index.sum { |ing, idx| perm[idx] * ing[property] }
+      total_score * [score, 0].max
+    end
+
+    calories = ingredients.each_with_index.sum { |ing, idx| perm[idx] * ing.calories }
+
+    [total_score, calories]
+  end
+end
+
+def main(file_paths)
+  file_paths.each do |file_path|
+    puts "File: #{file_path}"
+    ingredients = parse_file(file_path)
+
+    scores = calculate_scores(ingredients)
+
+    solution1 = scores.max_by { |(score, _)| score }.first
+    puts "  solution 1: #{solution1}"
+
+    solution2 = scores.select { |(_, cal)| cal == 500 }.max_by { |(score, _)| score }.first
+    puts "  solution 2: #{solution2}"
+  end
+end
+
+main(ARGV.map { |x| Pathname(x) })