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.
61 lines
1.7 KiB
Racket
61 lines
1.7 KiB
Racket
#lang br
|
|
(require racket/file rackunit)
|
|
|
|
(define (lex-1 port)
|
|
(match (regexp-match #rx"^se|nw|sw|ne|w|e" port)
|
|
[#false eof]
|
|
[(list str) str]))
|
|
|
|
(define tokss (for/list ([ln (in-list (file->lines "24.rktd"))])
|
|
(for/list ([tok (in-port lex-1 (open-input-string ln))])
|
|
tok)))
|
|
|
|
(define (tok->delta tok)
|
|
(match tok
|
|
[#"w" -1]
|
|
[#"e" 1]
|
|
[#"nw" -i]
|
|
[#"ne" 1-i]
|
|
[#"sw" -1+i]
|
|
[#"se" +i]))
|
|
|
|
(define white -1)
|
|
(define black 1)
|
|
(define black? positive?)
|
|
|
|
(define (make-initial-floor tokss)
|
|
(define floor (make-hasheqv))
|
|
(for ([toks (in-list tokss)])
|
|
(hash-update! floor (apply + (map tok->delta toks)) - white))
|
|
floor)
|
|
|
|
(define deltas '(1 -1 -i 1-i -1+i +i))
|
|
|
|
(define (grow! floor)
|
|
(for* ([k (in-list (hash-keys floor))]
|
|
[delta (in-list deltas)])
|
|
(hash-ref! floor (+ k delta) white)))
|
|
|
|
(define (adjacent-black-tiles floor k)
|
|
(for/sum ([delta (in-list deltas)]
|
|
#:when (black? (hash-ref floor (+ k delta) white)))
|
|
1))
|
|
|
|
(define (iterate floor num)
|
|
(for ([i (in-range num)])
|
|
(grow! floor)
|
|
(define fliplist
|
|
(for/list ([(k v) (in-hash floor)]
|
|
#:when (let ([abt (adjacent-black-tiles floor k)])
|
|
(cond
|
|
[(and (black? v) (or (zero? abt) (< 2 abt)))]
|
|
[(and (not (black? v)) (= 2 abt))]
|
|
[else #false])))
|
|
k))
|
|
(for ([k (in-list fliplist)])
|
|
(hash-update! floor k -)))
|
|
floor)
|
|
|
|
(define floor (make-initial-floor tokss))
|
|
(check-equal? (count black? (hash-values floor)) 436)
|
|
(check-equal? (count black? (hash-values (iterate floor 100))) 4133) |