aoc2022/3.rkt

#lang curly-fn racket

(require "scripts/aoc.rkt")

;; solution for day 3

(define priorities
  (string->list "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"))

(define (part1 input)
  (for/sum ([line (in-list input)])
    (define-values [left right] (split-at line (/ (length line) 2)))
    (~>> (set-intersect left right)
         (set-first)
         (index-of priorities))))

(define (part2 input)
  (match input
    ['() 0]
    [(list* a b c rst)
     (+ (~>> (set-intersect a b c)
             (set-first)
             (index-of priorities))
        (part2 rst))]))

(define (parse fname)
  (map string->list (file->lines fname)))

(module+ main
  (define input (parse "inputs/3"))
  (answer 3 1 (time (part1 input)))
  (answer 3 2 (time (part2 input)))
  (displayln "meow"))