day 14 tweaks

1 files changed, 30 insertions, 45 deletions

diff --git a/2022/day-14/day-14.rkt b/2022/day-14/day-14.rkt
index 7950339..c6b5c88 100644
--- a/2022/day-14/day-14.rkt
+++ b/2022/day-14/day-14.rkt
@@ -8,57 +8,42 @@
 
 (define (trace-line-between-points p1 p2)
   (match* (p1 p2)
-    [((list x y1) (list x y2))
-     (for/list ([y [in-inclusive-range (min y1 y2) (max y1 y2)]])
-       (cons x y))]
-    [((list x1 y) (list x2 y))
-     (for/list ([x [in-inclusive-range (min x1 x2) (max x1 x2)]])
-       (cons x y))]))
+    [((list x y1) (list x y2)) (map (λ (y) (cons x y)) (inclusive-range (min y1 y2) (max y1 y2)))]
+    [((list x1 y) (list x2 y)) (map (λ (x) (cons x y)) (inclusive-range (min x1 x2) (max x1 x2)))]))
 
-(define all-coordinates
-  (apply append
-         (for/list ([formation (in-list (string-split data "\n"))])
-           (define coord-list
-             (for/list ([coord-pair (in-list (string-split formation " -> "))])
-               (for/list ([coord (in-list (string-split coord-pair ","))])
-                 (string->number coord))))
-           (apply append (adjacent-map trace-line-between-points coord-list)))))
+(define (find-points-in-structure str)
+  (define endpoints
+    (for/list ([coord-pair (in-list (string-split str " -> "))])
+      (for/list ([coord (in-list (string-split coord-pair ","))])
+        (string->number coord))))
+  (~>> endpoints (adjacent-map trace-line-between-points) (apply append) (list->set)))
 
-(define rock-structures-hash
-  (for/hash ([p (in-list all-coordinates)])
-    (values p 'rock)))
+(define blocked-locations
+  (~> data (string-split "\n") (map find-points-in-structure _) (apply set-union _)))
 
-(define max-vertical-distance (~>> all-coordinates (argmax cdr) cdr add1))
+(define max-vertical-distance (~>> blocked-locations (set->list) (argmax cdr) cdr add1))
 
-(define (open? h x y)
-  (not (hash-has-key? h (cons x y))))
+(define (open? pts p)
+  (not (set-member? pts p)))
 
 ;; part 1
-(define (trace-grain h [pos (cons 500 0)])
-  (match-define (cons x y) pos)
+(define (trace-grain pts [pt (cons 500 0)] #:at-limit do-at-limit)
+  (match-define (cons x y) pt)
   (cond
-    [(> y max-vertical-distance) 'break]
-    [(open? h x (add1 y)) (trace-grain h (cons x (add1 y)))]
-    [(open? h (sub1 x) (add1 y)) (trace-grain h (cons (sub1 x) (add1 y)))]
-    [(open? h (add1 x) (add1 y)) (trace-grain h (cons (add1 x) (add1 y)))]
-    [else (hash-set h (cons x y) 'sand)]))
-
-(for/fold ([h rock-structures-hash] [grains 0] #:result grains) ([_ (in-naturals 1)])
-  (define h* (trace-grain h))
-  #:break (eq? h* 'break)
-  (values h* (add1 grains)))
+    [(>= y max-vertical-distance) (do-at-limit pts pt)]
+    [(ormap (λ (d)
+              (let ([p* (cons (+ x d) (add1 y))])
+                (if (open? pts p*) (trace-grain pts p* #:at-limit do-at-limit) #f)))
+            '(0 -1 1))]
+    [else (set-add pts pt)]))
+
+(for/fold ([pts blocked-locations] [grains 0] #:result grains) ([_ (in-naturals 1)])
+  (define pts* (trace-grain pts #:at-limit (const 'break)))
+  #:break (equal? pts* 'break)
+  (values pts* (add1 grains)))
 
 ;; part 2
-(define (trace-grain* h [pos (cons 500 0)])
-  (match-define (cons x y) pos)
-  (cond
-    [(= y max-vertical-distance) (hash-set h (cons x y) 'sand)]
-    [(open? h x (add1 y)) (trace-grain* h (cons x (add1 y)))]
-    [(open? h (sub1 x) (add1 y)) (trace-grain* h (cons (sub1 x) (add1 y)))]
-    [(open? h (add1 x) (add1 y)) (trace-grain* h (cons (add1 x) (add1 y)))]
-    [else (hash-set h (cons x y) 'sand)]))
-
-(for/fold ([h rock-structures-hash] [grains 0] #:result grains) ([_ (in-naturals 1)])
-  #:break (not (open? h 500 0))
-  (define h* (trace-grain* h))
-  (values h* (add1 grains)))
+(for/fold ([pts blocked-locations] [grains 0] #:result grains) ([_ (in-naturals 1)])
+  #:break (not (open? pts (cons 500 0)))
+  (define pts* (trace-grain pts #:at-limit set-add))
+  (values pts* (add1 grains)))