Project Euler Problem 11

pep011.clj

(require '[clojure.string :as s])
(require '[clojure.test :refer (deftest run-tests is)])
 
(defn trans [[& rows]] (apply (partial map list) rows))
 
(defn flip [mat] (map reverse mat))
 
(defn rot45 [mat]
  (let [w (count (first mat))
        h (count mat)
        r-mat (reverse mat)]
    (map (partial remove nil?)
      (for [i (range (- 1 h) w)]
        (map #(get (vec %) %2) r-mat (iterate inc i))))))
 
(deftest test-mat-utils
  (let [mat '((a b c d)
              (e f g h)
              (i j k l))]
    (is (= (trans mat)
           '((a e i)
             (b f j)
             (c g k)
             (d h l))))
    (is (= (flip mat)
           '((d c b a)
             (h g f e)
             (l k j i))))
    (is (= (rot45 mat)
           '((  a   )
             ( e b  )
             (i f c )
             ( j g d)
             (  k h )
             (   l  ))))))
 
(defn text2mat
  [conv ; converter for each column
   fs   ; field separater in regular expression
   rs   ; record separater in regular expression
   text]
  (map #(map conv %) (map #(s/split % fs) (s/split text rs))))
 
(deftest test-text2mat
  (is (= (text2mat (fn [^String s] (.toUpperCase s))
           #"," #"\n" "a,b,c,\nd,e,f,\ng,h,i,\n")
         '(("A" "B" "C")
           ("D" "E" "F")
           ("G" "H" "I"))))
  (is (= (text2mat #(Integer/parseInt %) #"\s" #"\n" (s/trim "
11 12 13
21 22 23
31 32 33
           "))
         '((11 12 13)
           (21 22 23)
           (31 32 33)))))
 
(def input "
08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08
49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00
81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65
52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 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 03 45 02 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 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21
24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72
21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95
78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92
16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57
86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58
19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40
04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66
88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69
04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36
20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16
20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54
01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48
")
 
(defn pep011
  ([] (pep011 4 input))
  ([n text]                  ; for example n 2 text "1 2 3\n4 5 6\n7 8 9"
    (let [mat (text2mat #(Integer/parseInt %) #"\s" #"\n" (s/trim text))]
                                         ; mat '((1 2 3) (4 5 6) (7 8 9))
      (->> (concat                       ; '(
             mat                         ;   (1 2 3) (4 5 6) (7 8 9)
             (trans mat)                 ;   (1 4 7) (2 5 8) (3 6 9)
             (rot45 mat)                 ;   (1) (4 2) (7 5 3) (8 6) (9)
             (rot45 (flip mat)))         ;   (3) (6 2) (9 5 1) (8 4) (7))
        (mapcat (partial partition n 1)) ; '((1 2) (2 3) ... (5 1) (8 4))
        (map (partial apply *))          ; '(2 6 ... 5 32)
        (apply max)))))                  ; 72
 
(deftest test-pep011
  (is (= (pep011 2 "
3 1 4
1 5 9
2 6 5
")
         54))
  (is (= (pep011 3 "
3 1 4 1
5 9 2 6
5 3 5 8
")
         180)))
       
(pep011)

@tnoda さん.
確かに, nil 除去なら filter identity より remove nil? の方が意図が伝わり易いですね.
そうさせていただきます.

インデックスに頼るのは苦手なので，私だったらどう書くか，．．．というのをちょっと考えてみます．

作ってみました． http://tnoda-clojure.tumblr.com/post/39856946125/2-45