(ns aocclj.day03
  (:require [clojure.string :as str]
            [clojure.set :as set]))

(defn priority [c]
  (->>
   (if (Character/isLowerCase c)
     (dec (int \a))
     (- (int \A) 27))
   (- (int c))))

(defn seq-halver [s]
  (split-at (/ (count s) 2) s))

(defn block-priority [block]
  ((comp priority first (partial apply set/intersection) (partial map set)) block))

(defn solver [group-transducer input]
  (transduce
   (comp
    group-transducer
    (map block-priority))
   + input))

(defn part1 [input]
  (solver (map seq-halver) input))

(defn part2 [input]
  (solver (partition-all 3) input))