1 files changed, 63 insertions, 0 deletions
diff --git a/day14.rkt b/day14.rkt
new file mode 100644
index 0000000..2e5f32f
--- /dev/null
+++ b/day14.rkt
@@ -0,0 +1,63 @@
+#lang racket
+
+(define area (build-vector 800 (lambda _ (make-vector 800 0))))
+
+(define (area-get x y)
+  (vector-ref (vector-ref area y) x))
+
+(define (area-set! x y v)
+  (vector-set! (vector-ref area y) x v))
+
+(define/match (draw from to)
+  [((list x y1) (list x y2))
+   (for ([y (in-inclusive-range (min y1 y2) (max y1 y2))])
+     (area-set! x y 9))]
+  [((list x1 y) (list x2 y))
+   (for ([x (in-inclusive-range (min x1 x2) (max x1 x2))])
+     (area-set! x y 9))])
+
+(for ([line (file->lines "day14")])
+  (let ([coords (for/list ([coord (string-split line " -> ")])
+                  (map string->number (string-split coord ",")))])
+    (for ([from coords]
+          [to (cdr coords)])
+      (draw from to))))
+
+(define (drop-sand x y)
+  (if (or (>= y 799) (>= x 799))
+    #f
+    (case (area-get x (+ y 1))
+      [(0)   (drop-sand x (+ y 1))]
+      [(1 9) (case (area-get (- x 1) (+ y 1))
+               [(0)   (drop-sand (- x 1) (+ y 1))]
+               [(1 9) (case (area-get (+ x 1) (+ y 1))
+                        [(0)   (drop-sand (+ x 1) (+ y 1))]
+                        [(1 9) (area-set! x y 1)])])])))
+
+(let loop ([i 0])
+  (if (drop-sand 500 0)
+    (loop (+ 1 i))
+    i))
+;; 665
+
+;; clear sand
+(void
+ (vector-map! (lambda (line) (vector-map! (lambda (x) (if (= x 1) 0 x)) line)) area))
+
+(void 
+ (for/and ([i (in-inclusive-range 599 0 -1)])
+   (when (for/or ([item (vector-ref area i)])
+           (= item 9))
+     (draw (list 0 (+ i 2))
+           (list 799 (+ i 2)))
+     #f)))
+
+(let loop ([i 0])
+  (if (= (area-get 500 0) 1)
+    i
+    (begin
+      (drop-sand 500 0)
+      (loop (+ 1 i)))))
+;; 25434
+
+;; (for ([line area]) (displayln line))