euler-008.clj

(in-ns 'project-euler)
(clojure.core/use 'clojure.core)

(def thousand-digit-number (apply str (replace {\newline nil \space nil} 
"73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450")))

(defn product-of-string 
  "Outputs the product of all single digit numbers in a string"
  [string]
  (apply * (map #(Integer/parseInt (str %)) (replace {} string))))

(loop [counter 0 highest 0]
  (if (> counter 1000) 
    (print highest)
		(let [
			counter-end 
			(if (> (+ counter 5) (count thousand-digit-number)) 
				(count thousand-digit-number) (+ counter 5)) 
			multiplied 
			(product-of-string (subs thousand-digit-number counter counter-end))]
	   	(if (> multiplied highest) 
	   	  (recur (+ counter 1) multiplied)
				(recur (+ counter 1) highest)))))