Project Euler in Clojure – Problem 8

This is my solution to Problem 8 of Project Euler. If you would like to track my progress you can follow my repository on github.com to keep track of my progress, which can be found at https://github.com/stevenproctor/project-euler-clojure.  Here is my solution to Problem 7.

Problem 8 of Project Euler is described as:

Find the greatest product of five consecutive digits in the 1000-digit number.
          73167176531330624919225119674426574742355349194934
          96983520312774506326239578318016984801869478851843
          85861560789112949495459501737958331952853208805511
          12540698747158523863050715693290963295227443043557
          66896648950445244523161731856403098711121722383113
          62229893423380308135336276614282806444486645238749
          30358907296290491560440772390713810515859307960866
          70172427121883998797908792274921901699720888093776
          65727333001053367881220235421809751254540594752243
          52584907711670556013604839586446706324415722155397
          53697817977846174064955149290862569321978468622482
          83972241375657056057490261407972968652414535100474
          82166370484403199890008895243450658541227588666881
          16427171479924442928230863465674813919123162824586
          17866458359124566529476545682848912883142607690042
          24219022671055626321111109370544217506941658960408
          07198403850962455444362981230987879927244284909188
          84580156166097919133875499200524063689912560717606
          05886116467109405077541002256983155200055935729725
          71636269561882670428252483600823257530420752963450

(defn digits-of [n]
  (map #(Integer/parseInt (str %)) (str n)))

(defn problem8 []
  (let [n 7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450]
    (apply max (map
                 #(apply * %) (partition 5 1 (digits-of n))))))

The digits-of function takes a number and creates a sequence of the digits of the number, in the same way a string can be treated as a sequence of characters. I then call partition on that stream of digits to get the digits in groups of five. Those groups of five get multiplied together, and we find the max of those results.

Again, I would love comments and suggestions on my solution to this problem, and if there are tweaks to make it more Clojure-ish.

**Update**
I have posted my solution to Problem 9.

–Proctor

5 thoughts on “Project Euler in Clojure – Problem 8

  1. Pingback: Project Euler in Clojure – Problem 7 « Proctor It

  2. Ankur

    Take the long number as string as that would make your to use only parseInt and you can avoid the (str n) call in the first function

    Reply
  3. Pingback: Project Euler in Clojure – Problem 9 « Proctor It

  4. Pingback: Project Euler in Clojure – Problem 13 « Proctor It

  5. Pingback: Project Euler in Clojure – Problem 16 « Proctor It

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