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aoc-racket/2021/06.rkt

18 lines
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Racket

2 years ago
#lang br
(require racket/file sugar rackunit)
(define fish (map string->number (string-split (file->string "06.rktd") ",")))
(define (simulate fish days)
(for/fold ([freqs (frequency-hash fish)]
#:result (apply + (hash-values freqs)))
([d (in-range days)])
(hash-set*
(for/hasheq ([(k v) (in-hash freqs)]
#:unless (zero? k))
(values (sub1 k) v))
6 (+ (hash-ref freqs 7 0) (hash-ref freqs 0 0))
8 (hash-ref freqs 0 0))))
(check-equal? (simulate fish 80) 361169)
(check-equal? (simulate fish 256) 1634946868992)