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Day 20 minor refactoring.

This commit is contained in:
Jonathan Chan 2020-12-20 17:47:00 -08:00 committed by Jonathan Chan
parent 83be0e883b
commit 178c6ab04f
1 changed files with 56 additions and 43 deletions
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99
src/20.rkt
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@ -105,61 +105,74 @@
[image (map #{drop-right (drop % 1) 1} (drop-right (drop image 1) 1))])
(map append rows image))))))
(define dimsize (length image))
(define image-vectors (lists->vectors image))
(define (vector-pos r c) (vector-ref (vector-ref image-vectors r) c))
;; Some vector grid helpers
;; N.B. coord? = (row, column) = (list number? number?)
;; lists->vectors: (listof (listof a)) -> (vectorof (vectorof a))
(define (lists->vectors list-grid)
(list->vector (map list->vector list-grid)))
;; vectors->lists: (vectorof (vectorof a)) -> (listof (listof a))
(define (vectors->lists vector-grid)
(vector->list (vector-map vector->list vector-grid)))
;; vector-grid-ref: (vectorof (vectorof a)) coord -> a
(define (vector-grid-ref vector-grid coord)
(vector-ref (vector-ref vector-grid (first coord)) (second coord)))
;; vector-grid-set!: (vectorof (vectorof a)) coord a -> void
(define (vector-grid-set! vector-grid coord v)
(vector-set! (vector-ref vector-grid (first coord)) (second coord) v))
#| (r, c) = O
#
# ## ## O## <--- friend
# # # # # #
|#
(define (sea-monster-coords r c)
(list `(,(- r 1) ,(+ c 1))
`(,r ,c)
`(,r ,(+ c 1))
`(,r ,(+ c 2))
`(,r ,(- c 5))
`(,r ,(- c 6))
`(,r ,(- c 11))
`(,r ,(- c 12))
`(,r ,(- c 17))
`(,(+ r 1) ,(- c 1))
`(,(+ r 1) ,(- c 4))
`(,(+ r 1) ,(- c 7))
`(,(+ r 1) ,(- c 10))
`(,(+ r 1) ,(- c 13))
`(,(+ r 1) ,(- c 16))))
(define (sea-monster-coords coord)
(match-let ([(list r c) coord])
(list `(,r ,c)
`(,r ,(+ c 1))
`(,r ,(+ c 2))
`(,(- r 1) ,(+ c 1))
`(,r ,(- c 5))
`(,r ,(- c 6))
`(,r ,(- c 11))
`(,r ,(- c 12))
`(,r ,(- c 17))
`(,(+ r 1) ,(- c 1))
`(,(+ r 1) ,(- c 4))
`(,(+ r 1) ,(- c 7))
`(,(+ r 1) ,(- c 10))
`(,(+ r 1) ,(- c 13))
`(,(+ r 1) ,(- c 16)))))
;; sea-monster?: number? number? -> boolean?
(define (sea-monster? r c)
(define (pound? c) (char=? c #\#))
(andmap #{pound? (vector-pos (first %) (second %))}
(sea-monster-coords r c)))
;; sea-monster?: coord? -> boolean?
(define (sea-monster? image-vectors coord)
(andmap #{char=? (vector-grid-ref image-vectors %) #\#}
(sea-monster-coords coord)))
;; A list of the neck coordinates of sea monsters
;; sea-monsters: (listof (list number? number?))
(define sea-monsters
(for*/list ([r (range 1 (sub1 dimsize))]
[c (range 17 (- dimsize 2))]
#:when (and (andmap #{char=? (vector-pos r %)}
(range c (+ c 3)))
(sea-monster? r c)))
(list r c)))
(let ([image-vectors (lists->vectors image)]
[dimsize (length image)])
(for*/list ([r (range 1 (sub1 dimsize))]
[c (range 17 (- dimsize 2))]
#:when (sea-monster? image-vectors (list r c)))
(list r c))))
;; Replace the # of a sea monster with O in image-vectors
(define (reveal-sea-monster! r c)
(for-each #{vector-set! (vector-ref image-vectors (first %)) (second %) #\O}
(sea-monster-coords r c)))
;; Reveal the sea monsters in image-vectors, then write to file
;; Draw sea monsters in O and write to file
(define (draw-sea-monsters!)
(for-each #{reveal-sea-monster! (first %) (second %)} sea-monsters)
(display-lines-to-file
(map (λ~> vector->list list->string)
(vector->list image-vectors))
"../input/20-image.txt"
#:exists 'replace))
(let ([image-vectors (lists->vectors image)])
(for* ([sea-monster sea-monsters]
[coord (sea-monster-coords sea-monster)])
(vector-grid-set! image-vectors coord #\O))
(display-lines-to-file
(map list->string
(vectors->lists image-vectors))
"../input/20-image.txt"
#:exists 'replace)))
(define part1
(* (tile-name (hash-ref image-hash (list 0 0)))
@ -169,6 +182,6 @@
(define part2
(- (count #{char=? % #\#} (apply append image))
(* (length sea-monsters) 15)))
(* (length sea-monsters) (length (sea-monster-coords (list 0 0))))))
(show-solution part1 part2)