euler11-opt.clj

(def grid [[8 2 22 97 38 15 0 40 0 75 4 5 7 78 52 12 50 77 91 8]
           [49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 4 56 62 0]
           [81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 3 49 13 36 65]
           [52 70 95 23 4 60 11 42 69 24 68 56 1 32 56 71 37 2 36 91]
           [22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80]
           [24 47 32 60 99 3 45 2 44 75 33 53 78 36 84 20 35 17 12 50]
           [32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70]
           [67 26 20 68 2 62 12 20 95 63 94 39 63 8 40 91 66 49 94 21]
           [24 55 58 5 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72]
           [21 36 23 9 75 0 76 44 20 45 35 14 0 61 33 97 34 31 33 95]
           [78 17 53 28 22 75 31 67 15 94 3 80 4 62 16 14 9 53 56 92]
           [16 39 5 42 96 35 31 47 55 58 88 24 0 17 54 24 36 29 85 57]
           [86 56 0 48 35 71 89 7 5 44 44 37 44 60 21 58 51 54 17 58]
           [19 80 81 68 5 94 47 69 28 73 92 13 86 52 17 77 4 89 55 40]
           [4 52 8 83 97 35 99 16 7 97 57 32 16 26 26 79 33 27 98 66]
           [88 36 68 87 57 62 20 72 3 46 33 67 46 55 12 32 63 93 53 69]
           [4 42 16 73 38 25 39 11 24 94 72 18 8 46 29 32 40 62 76 36]
           [20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 4 36 16]
           [20 73 35 29 78 31 90 1 74 31 49 71 48 86 81 16 23 57 5 54]
           [1 70 54 71 83 51 54 69 16 92 33 48 61 43 52 1 89 19 67 48]])

(def directions [[0 -1] [1 0] [1 -1]])

(defn product [coord dir grid]
  (->> coord
       (iterate #(map + % dir))
       (map #(get-in grid % 0))
       (take 4)
       (reduce *)))

(defn greatest-product [coord grid]
  (->> directions
       (map #(product coord % grid))
       (apply max)))

(defn all-greatest-products [grid]
  (for [x (range 1 16) y (range 1 16)]
    (greatest-product [x y] grid)))

(->> (all-greatest-products grid)
     (apply max)
     (println))