1 files changed, 49 insertions, 0 deletions
diff --git a/racket/aoc2015/day-06/day-06.rkt b/racket/aoc2015/day-06/day-06.rkt
new file mode 100644
index 0000000..d2eed08
--- /dev/null
+++ b/racket/aoc2015/day-06/day-06.rkt
@@ -0,0 +1,49 @@
+#lang racket
+(require "../../jj-aoc.rkt"
+         threading)
+
+(struct instruction (todo x1 y1 x2 y2) #:transparent)
+
+(define (make-instruction lst)
+  (apply instruction (string->symbol (first lst)) (map string->number (rest lst))))
+
+(define instructions
+  (for/list ([l (in-lines (open-day 6 2015))])
+    (~>> l
+         (regexp-match
+          #px"(turn on|toggle|turn off) (\\d{1,3}),(\\d{1,3}) through (\\d{1,3}),(\\d{1,3})")
+         rest
+         make-instruction)))
+
+(define (vector2d-modify! vec x y f)
+  (define pos (+ x (* 1000 y)))
+  (vector-set! vec pos (f (vector-ref vec pos))))
+
+;; part 1
+(define (todo inst)
+  (match (instruction-todo inst)
+    ['|turn on| (λ _ #true)]
+    ['|turn off| (λ _ #false)]
+    ['|toggle| not]))
+
+(define (modify-light-grid inst light-grid using)
+  (for ([x (inclusive-range (instruction-x1 inst) (instruction-x2 inst))])
+    (for ([y (inclusive-range (instruction-y1 inst) (instruction-y2 inst))])
+      (vector2d-modify! light-grid x y (using inst)))))
+
+(define light-grid (make-vector (* 1000 1000) #false))
+(for ([i (in-list instructions)])
+  (modify-light-grid i light-grid todo))
+(vector-count identity light-grid)
+
+;; part 2
+(define (todo-dimmer inst)
+  (match (instruction-todo inst)
+    ['|turn on| add1]
+    ['|turn off| (λ (x) (max 0 (sub1 x)))]
+    ['|toggle| (curry + 2)]))
+
+(define dimmable-grid (make-vector (* 1000 1000) 0))
+(for ([i (in-list instructions)])
+  (modify-light-grid i dimmable-grid todo-dimmer))
+(apply + (vector->list dimmable-grid))