adv2015_day06.clj

(def W 1000)
(def input (clojure.string/split-lines (slurp "d06.txt")))
(let [lights (boolean-array (* W W))]
  (doseq [s input]
    (let [ m (re-matches #"(turn on|turn off|toggle) (\d+),(\d+) through (\d+),(\d+)" s)
           command (get m 1)
           x1 (Integer/parseInt (get m 2))
           y1 (Integer/parseInt (get m 3))
           x2 (Integer/parseInt (get m 4))
           y2 (Integer/parseInt (get m 5)) ]
      (cond
        (= command "turn on")
        (doseq [ x (range x1 (inc x2))
                 y (range y1 (inc y2))
                 :let [i (+ (* y W) x)] ]
          (aset lights i true))
        (= command "turn off")
        (doseq [ x (range x1 (inc x2))
                 y (range y1 (inc y2))
                 :let [i (+ (* y W) x)] ]
          (aset lights i false))
        (= command "toggle")
        (doseq [ x (range x1 (inc x2))
                 y (range y1 (inc y2))
                 :let [i (+ (* y W) x)] ]
          (aset lights i (not (aget lights i))))
        )))
  (printf "%d\n" (count (filter identity lights))))