diff options
Diffstat (limited to '2021/day-09/day-09.rkt')
| -rw-r--r-- | 2021/day-09/day-09.rkt | 47 |
1 files changed, 14 insertions, 33 deletions
diff --git a/2021/day-09/day-09.rkt b/2021/day-09/day-09.rkt index 7c55d43..d550a9e 100644 --- a/2021/day-09/day-09.rkt +++ b/2021/day-09/day-09.rkt @@ -4,12 +4,8 @@ "../../jj-aoc.rkt") (define sea-floor-data - (for/vector ([l (in-lines (open-day 9))] - #:unless (equal? l "")) - (~>> l - string->list - (map (λ~>> ~a string->number)) - list->vector))) + (for/vector ([l (in-lines (open-day 9))] #:unless (equal? l "")) + (~>> l string->list (map (λ~>> ~a string->number)) list->vector))) (define max-rows (vector-length sea-floor-data)) (define max-cols (vector-length (vector-ref sea-floor-data 0))) @@ -17,35 +13,25 @@ (define (vector2d-ref vec coord) (match-define `(,r ,c) coord) - (~> vec - (vector-ref r) - (vector-ref c))) + (~> vec (vector-ref r) (vector-ref c))) (define (adjacent coords) (match-define `(,r ,c) coords) - `((,(add1 r) ,c) - (,(sub1 r) ,c) - (,r ,(add1 c)) - (,r ,(sub1 c)))) + `((,(add1 r) ,c) (,(sub1 r) ,c) (,r ,(add1 c)) (,r ,(sub1 c)))) (define (valid-coordinate coord) (match-define `(,r ,c) coord) - (and (>= r min-rows) - (< r max-rows) - (>= c min-cols) - (< c max-cols))) + (and (>= r min-rows) (< r max-rows) (>= c min-cols) (< c max-cols))) ;; part 1 (define (lowest-point? vec coord) - (for*/and ([neighbor (in-list (adjacent coord))] - #:when (valid-coordinate neighbor)) + (for*/and ([neighbor (in-list (adjacent coord))] #:when (valid-coordinate neighbor)) (< (vector2d-ref vec coord) (vector2d-ref vec neighbor)))) -(for*/sum ([r (in-range min-rows max-rows)] - [c (in-range min-cols max-cols)] - [coord (in-value `(,r ,c))] - #:when (lowest-point? sea-floor-data coord)) - (add1 (vector2d-ref sea-floor-data coord))) +(for*/sum ([r (in-range min-rows max-rows)] [c (in-range min-cols max-cols)] + [coord (in-value `(,r ,c))] + #:when (lowest-point? sea-floor-data coord)) + (add1 (vector2d-ref sea-floor-data coord))) ;; part 2 ;; all the basins are bordered by the edges or by ridges of elevation 9, @@ -53,16 +39,14 @@ (define walked (make-hash)) (define (walkable? vec coord) - (and (< (vector2d-ref vec coord) 9) - (not (hash-has-key? walked coord)))) + (and (< (vector2d-ref vec coord) 9) (not (hash-has-key? walked coord)))) (define (walk-the-basin vec coord) (cond [(walkable? vec coord) (hash-set! walked coord 'visited) - (add1 (for/sum [(neighbor (in-list (adjacent coord))) - #:when (valid-coordinate neighbor)] - (walk-the-basin vec neighbor)))] + (add1 (for/sum [(neighbor (in-list (adjacent coord))) #:when (valid-coordinate neighbor)] + (walk-the-basin vec neighbor)))] [else 0])) (define basins @@ -72,7 +56,4 @@ #:when (walkable? sea-floor-data coord)) (walk-the-basin sea-floor-data coord))) -(~> basins - (sort >) - (take 3) - (apply * _))
\ No newline at end of file +(~> basins (sort >) (take 3) (apply * _)) |