diff options
Diffstat (limited to 'aoc2023-other/day-09/day-09.rkt')
| -rw-r--r-- | aoc2023-other/day-09/day-09.rkt | 20 |
1 files changed, 15 insertions, 5 deletions
diff --git a/aoc2023-other/day-09/day-09.rkt b/aoc2023-other/day-09/day-09.rkt index c632150..5eda1eb 100644 --- a/aoc2023-other/day-09/day-09.rkt +++ b/aoc2023-other/day-09/day-09.rkt @@ -5,18 +5,28 @@ (define histories (for/list ([raw-history (in-lines (open-aoc-input (find-session) 2023 9 #:cache #true))]) - (~>> raw-history string-split (map string->number)))) + (~>> raw-history + string-split + (map string->number)))) -(define (constant? xs) (= 1 (length (remove-duplicates xs)))) +(define (constant? xs) + (= 1 (length (remove-duplicates xs)))) (define/match (derivative xs) [((list a b)) (list (- b a))] [((list* a b _)) (cons (- b a) (derivative (rest xs)))]) -(define (extrapolate xs) (if (constant? xs) (car xs) (+ (last xs) (extrapolate (derivative xs))))) +(define (extrapolate xs) + (if (constant? xs) + (car xs) + (+ (last xs) (extrapolate (derivative xs))))) ;; part 1 -(~>> histories (map extrapolate) (apply +)) +(~>> histories + (map extrapolate) + (apply +)) ;; part 2 -(~>> histories (map (λ~> reverse extrapolate)) (apply +)) +(~>> histories + (map (λ~> reverse extrapolate)) + (apply +)) |