aoc2022/3.rkt

#lang curly-fn racket

(require "scripts/aoc.rkt")

;; solution for day 3

(define (char->prio chr)
  (- (char->integer chr) (if (char-upper-case? chr) 38 96)))

(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) (char->prio))))

(define (part2 input)
  (for/sum ([group (in-slice 3 input)])
    (~> (apply set-intersect group) (set-first) (char->prio))))

(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"))