diff options
Diffstat (limited to 'aoc2023-racket/day-16/day-16.rkt')
| -rw-r--r-- | aoc2023-racket/day-16/day-16.rkt | 70 |
1 files changed, 0 insertions, 70 deletions
diff --git a/aoc2023-racket/day-16/day-16.rkt b/aoc2023-racket/day-16/day-16.rkt deleted file mode 100644 index 4a70de8..0000000 --- a/aoc2023-racket/day-16/day-16.rkt +++ /dev/null @@ -1,70 +0,0 @@ -#lang racket - -(require advent-of-code - threading) - -(struct posn (r c) #:transparent) -(struct light (posn dir) #:transparent) - -(define input (fetch-aoc-input (find-session) 2023 16 #:cache #true)) - -(define grid - (for*/hash ([(row r) (in-indexed (string-split input "\n"))] - [(cell c) (in-indexed (in-string row))]) - (values (posn r c) cell))) - -(define/match (move _l) - [((light (posn r c) 'up)) (light (posn (sub1 r) c) 'up)] - [((light (posn r c) 'right)) (light (posn r (add1 c)) 'right)] - [((light (posn r c) 'left)) (light (posn r (sub1 c)) 'left)] - [((light (posn r c) 'down)) (light (posn (add1 r) c) 'down)]) - -(define/match (transform l _cell) - [(_ #\.) l] - [(_ 'off) '()] - - [((light _ (or 'up 'down)) #\|) l] - [((light _ (or 'left 'right)) #\-) l] - - [((light p 'left) #\/) (light p 'down)] - [((light p 'down) #\/) (light p 'left)] - [((light p 'right) #\/) (light p 'up)] - [((light p 'up) #\/) (light p 'right)] - - [((light p 'left) #\\) (light p 'up)] - [((light p 'up) #\\) (light p 'left)] - [((light p 'right) #\\) (light p 'down)] - [((light p 'down) #\\) (light p 'right)] - - [((light p (or 'left 'right)) #\|) (list (light p 'up) (light p 'down))] - [((light p (or 'up 'down)) #\-) (list (light p 'left) (light p 'right))]) - -;; part 1 -(define (get-energized start) - (for/fold ([energized (set)] - [previously-visited (set)] - [beam-tips (set start)] - #:result (set-count energized)) - ([_ (in-naturals)]) - (define next-positions - (list->set - (flatten (for/list ([b (in-set beam-tips)]) - (~> b move ((λ (b) (transform b (hash-ref grid (light-posn b) 'off))))))))) - (define all-visited (set-union previously-visited next-positions)) - (define next-energized (set-union energized (list->set (set-map next-positions light-posn)))) - #:break (equal? previously-visited all-visited) - (values next-energized all-visited (set-subtract next-positions previously-visited)))) - -(get-energized (light (posn 0 -1) 'right)) - -;; part 2 -(define rows (~> input (string-split "\n") length)) -(define cols (~> input (string-split #rx"\n.*") first string-length)) - -(define all-starting-positions - (append (map (λ (r) (light (posn r -1) 'right)) (range rows)) - (map (λ (r) (light (posn r cols) 'left)) (range rows)) - (map (λ (c) (light (posn -1 c) 'down)) (range cols)) - (map (λ (c) (light (posn rows c) 'up)) (range cols)))) - -(get-energized (argmax get-energized all-starting-positions))
\ No newline at end of file |