amalloy-4clojure-solution127.clj

;; amalloy's solution to Love Triangle
;; https://4clojure.com/problem/127

(fn [m t e c i a r v g]
  (let [p (t #(<= % (m g))
             (i #(* 2 %) 1))
        H (c g)
        W (c p)
        g (v (for [y g]
               (v
                (for [x p]
                  (> (bit-and x y) 0)))))
        o #(and (e true?
                   (a < [-1 -1] % [H W]))
                (get-in g %))
        z (fn [s g]
            (->> #{s}
                 (i #(set
                      (mapcat g %)))
                 (t #(e o %))
                 (a c)
                 (apply +)))

        n [-1 0] ne [-1 1] e [0 1] se [1 1]
        s [1 0] sw [1 -1] w [0 -1] nw [-1 -1]

        t (for [x [[n e] [e s] [s w] [w n]
                   [nw n ne] [ne e se]
                   [sw s se] [nw w sw]]]
            (fn [p]
              (for [d x]
                (a + d p))))

        o (m
           (for [y (r H) x (r W)
                 g t]
             (z [y x] g)))]
    (when (>= o 3)
      o)))
#(apply max %)
take-while
every?
count
iterate
map
range
vec