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.
47 lines
1.5 KiB
Racket
47 lines
1.5 KiB
Racket
#lang debug br
|
|
(require racket/file)
|
|
|
|
(define (mlength mprs [acc 0])
|
|
(if (null? mprs)
|
|
acc
|
|
(mlength (mcdr mprs) (add1 acc))))
|
|
|
|
(define (nth-mpr mprs n)
|
|
(for/fold ([mprs mprs])
|
|
([i (in-range n)])
|
|
(mcdr mprs)))
|
|
|
|
(define (★)
|
|
(match-define (list player-count marble-count)
|
|
(map string->number (regexp-match* #px"\\d+" (file->string "09.txt"))))
|
|
(define scores (make-hasheqv))
|
|
(define circle (mcons #f (mcons 0 null)))
|
|
(let loop ([marble 1] [pos 0])
|
|
(cond
|
|
[(> marble marble-count) (argmax cdr (hash->list scores))]
|
|
[(zero? (modulo marble 23))
|
|
(define marble-count (sub1 (mlength circle)))
|
|
(define deletion-pos (modulo (+ (- pos 7) marble-count) marble-count))
|
|
(define last-left-mpr (nth-mpr circle deletion-pos))
|
|
(define removed-marble (mcar (mcdr last-left-mpr)))
|
|
(set-mcdr! last-left-mpr (mcdr (mcdr last-left-mpr)))
|
|
(define player (modulo marble player-count))
|
|
(hash-update! scores player (λ (sc) (+ removed-marble marble sc)) 0)
|
|
(loop (add1 marble) deletion-pos)]
|
|
[else
|
|
(define marble-count (sub1 (mlength circle)))
|
|
(define next-pos (add1 (modulo (add1 pos) marble-count)))
|
|
(define last-left-mpr (nth-mpr circle next-pos))
|
|
(set-mcdr! last-left-mpr (mcons marble (mcdr last-left-mpr)))
|
|
(loop (add1 marble) next-pos)])))
|
|
|
|
(time (★))
|
|
|
|
#;(define (★★)
|
|
)
|
|
#;(★★)
|
|
|
|
#;(module+ test
|
|
(require rackunit)
|
|
(check-equal? (time (★)) 437654)
|
|
(check-equal? (time (★★)) 566)) |