project-euler8.clj

(ns project-euler.core)

(def str "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450")

(defn divide-by [str n]
  (partition n 1 str))

(defn multiply [str]
  (apply * (for [x str] (Character/digit x 10))))

(defn find1 [str]
  (loop [lst (divide-by str 13)
         greatest 0
         str1 ""]
    (let [result (multiply (first lst))]
      (cond 
       (empty? lst) (list greatest str1)
       (> result greatest) (recur (rest lst) result (first lst))
       :else (recur (rest lst) greatest str1)))))

(find1 str)