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.
43 lines
1.4 KiB
Racket
43 lines
1.4 KiB
Racket
#lang br
|
|
(require racket/file rackunit)
|
|
|
|
(define grid
|
|
(for*/hasheqv ([(row ridx) (in-indexed (file->lines "11.rktd"))]
|
|
[(col cidx) (in-indexed row)])
|
|
(values (make-rectangular cidx ridx) col)))
|
|
|
|
(define (seat-count grid)
|
|
(count (λ (val) (char=? val #\#)) (hash-values grid)))
|
|
|
|
(define offsets '(-1-1i -1 -1+i +i 1+i 1 1-i -i))
|
|
|
|
(define (visible-occupied-seats grid k [adjacent-only? #false])
|
|
(for/sum ([offset (in-list offsets)])
|
|
(let loop ([k (+ k offset)] [sum 0])
|
|
(match (hash-ref grid k #false)
|
|
[#false sum]
|
|
[#\# 1]
|
|
[#\L 0]
|
|
[_ (if adjacent-only?
|
|
sum
|
|
(loop (+ k offset) sum))]))))
|
|
|
|
(define (adjacent-occupied-seats grid k) (visible-occupied-seats grid k #true))
|
|
|
|
(define (iterate grid seat-counter threshold)
|
|
(for/hasheqv ([(k v) (in-hash grid)])
|
|
(match v
|
|
[#\L #:when (zero? (seat-counter grid k)) (values k #\#)]
|
|
[#\# #:when (<= threshold (seat-counter grid k)) (values k #\L)]
|
|
[_ (values k v)])))
|
|
|
|
(define (solve grid iteration-proc)
|
|
(let loop ([grid grid])
|
|
(define next-grid (iteration-proc grid))
|
|
(if (eqv? (seat-count grid) (seat-count next-grid))
|
|
(seat-count grid)
|
|
(solve next-grid iteration-proc))))
|
|
|
|
(check-equal? (solve grid (λ (grid) (iterate grid adjacent-occupied-seats 4))) 2489)
|
|
|
|
(check-equal? (solve grid (λ (grid) (iterate grid visible-occupied-seats 5))) 2180) |