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author | H.J <thechairman@thechairman.info> | 2024-10-09 11:36:55 -0400 |
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committer | H.J <thechairman@thechairman.info> | 2024-10-09 11:36:55 -0400 |
commit | 8777ff071f7bb37631baa7b6717ad29961e50911 (patch) | |
tree | 6d59c4ed58e454b960339c3d1151f0a879e8d7cb /aoc2021/day-09/day-09.rkt | |
parent | 6156a9ef7be4012063a042aafb4e9b0d7eadde8e (diff) | |
download | gleam_aoc-8777ff071f7bb37631baa7b6717ad29961e50911.tar.gz gleam_aoc-8777ff071f7bb37631baa7b6717ad29961e50911.zip |
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Diffstat (limited to 'aoc2021/day-09/day-09.rkt')
-rw-r--r-- | aoc2021/day-09/day-09.rkt | 59 |
1 files changed, 0 insertions, 59 deletions
diff --git a/aoc2021/day-09/day-09.rkt b/aoc2021/day-09/day-09.rkt deleted file mode 100644 index d550a9e..0000000 --- a/aoc2021/day-09/day-09.rkt +++ /dev/null @@ -1,59 +0,0 @@ -#lang racket - -(require threading - "../../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))) - -(define max-rows (vector-length sea-floor-data)) -(define max-cols (vector-length (vector-ref sea-floor-data 0))) -(define-values (min-rows min-cols) (values 0 0)) - -(define (vector2d-ref vec coord) - (match-define `(,r ,c) coord) - (~> 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)))) - -(define (valid-coordinate coord) - (match-define `(,r ,c) coord) - (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)) - (< (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))) - -;; part 2 -;; all the basins are bordered by the edges or by ridges of elevation 9, -;; so it's not really necessary to start at a low point -(define walked (make-hash)) - -(define (walkable? vec 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)))] - [else 0])) - -(define basins - (for*/list ([r (in-range min-rows max-rows)] - [c (in-range min-cols max-cols)] - [coord (in-value `(,r ,c))] - #:when (walkable? sea-floor-data coord)) - (walk-the-basin sea-floor-data coord))) - -(~> basins (sort >) (take 3) (apply * _)) |