clojure-euler-4

gistfile1.clj

(import '(java.lang Math))

(defn palindrome? [n]
  (= (->> n str reverse (apply str))
     (str n)))

(defn test-for-products [n pmax pmin]
  (some #(let [p (/ n %)]
    (and (<= p pmax) (>= p pmin)))
    (for [i (range pmin (inc pmax)) :let [m (mod n i)] :when (= m 0)] i)))

(defn euler-4-largest-palindrome [max-digits]
   (let [max-product (dec (int (Math/pow 10 max-digits)))
         min-product (int (Math/pow 10 (dec max-digits)))
        ] 
     (first (for [i (range 
                        (* max-product max-product)
                        (* min-product min-product) -1)
                 :when (and (palindrome? i)
                            (test-for-products i max-product min-product))] 
            i))))

(time (euler-4-largest-palindrome 3))