advent-15.clj

(ns advent.a15
  (:require
   [clojure.string :as str]
   [clojure.core.logic :as l :refer [run run* fresh]]
   [clojure.core.logic.fd :as fd]))

(def text "Sugar: capacity 3, durability 0, flavor 0, texture -3, calories 2
Sprinkles: capacity -3, durability 3, flavOr 0, texture 0, calories 9
Candy: capacity -1, durability 0, flavor 4, texture 0, calories 1
Chocolate: capacity 0, durability 0, flavor -2, texture 2, calories 8")

(def test "Butterscotch: capacity -1, durability -2, flavor 6, texture 3, calories 8
Cinnamon: capacity 2, durability 3, flavor -2, texture -1, calories 3")

(defn parse-int [i]
  (Integer/parseInt i))

(defn parse [l]
  (let [ns (re-seq #"-?\d+" l)]
    (map parse-int ns)))

(defn rules [text]
  (map parse (str/split-lines text)))

(defn transpose [vss]
  (for [i (range (count (first vss)))]
    (for [vs vss]
      (nth vs i))))

(defn attrs [mults rules]
  (for [cat (transpose rules)]
    (map #(* %1 %2) mults cat)))

(defn score [mults rules]
  (let [attrs (attrs mults rules)
        vals (map (partial reduce +) attrs)]
    (if (some neg? vals) 0
        (reduce * vals))))

(defn mults [n [w x y z]]
  (run* [q]
    (fresh [a b c d]
      (fd/in a b c d (fd/interval 0 n))
      (fd/eq (= (+ a b c d) n)
             (= (+ (* a w) (* b x) (* c y) (* d z)) 500))
      (l/== q [a b c d]))))

(let [rules (rules text)
      vals (map butlast rules)
      cals (map last rules)
      mults (mults 100 cals)
      scores (for [m mults] (score m vals))]
  (apply max scores))