You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
This repo is archived. You can view files and clone it, but cannot push or open issues/pull-requests.
aoc-racket/2018/04.rkt

53 lines
1.6 KiB
Racket

This file contains invisible Unicode characters!

This file contains invisible Unicode characters that may be processed differently from what appears below. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to reveal hidden characters.

#lang debug br
(require sugar/list gregor)
(define fp (open-input-file "04.txt"))
(define (parse-rec ln)
(match (regexp-match #px"^(\\[.*?\\]) (.*)$" ln)
[(list _ datestr desc) (cons
(parse-datetime datestr "[yyyy-MM-dd HH:mm]")
desc)]))
(define recs
(map parse-rec (port->lines fp)))
(define (make-interval-hash recs)
(define intervals (make-hasheqv))
(for/fold ([guard #f]
[recs (sort recs datetime<? #:key car)]
#:result intervals)
([i (in-naturals)]
#:break (empty? recs))
(match (car recs)
[(cons dt "falls asleep")
(define other-dt (car (second recs)))
(define mins (range (->minutes dt) (->minutes other-dt)))
(hash-update! intervals guard (λ (val) (append mins val)) null)
(values guard (drop recs 2))]
[(cons _ (regexp #px"\\d+" m)) (values (string->number (car m)) (cdr recs))])))
(define (sleepiest h)
(argmax (compose1 length cdr) (hash->list h)))
(define (most-common-minute gms)
(argmax cdr (hash->list (frequency-hash gms))))
(define h (make-interval-hash recs))
(define ()
(match (sleepiest h)
[(cons guard minutes)
(match (most-common-minute minutes)
[(cons min _) (* guard min)])]))
(define (★★)
(define guard-min-freqs
(for/list ([(k v) (in-hash h)])
(match-define (cons min freq) (most-common-minute v))
(list k min freq)))
(apply * (take (argmax third guard-min-freqs) 2)))
(module+ test
(require rackunit)
(check-equal? (time ()) 99759)
(check-equal? (time (★★)) 97884))