Project Euler Problem #8

Largest products of five consecutive digits in this 1000-digit number.

open System.Numerics

let digits n = Seq.unfold (fun i –>
    if i = 0I then None
    else Some(i % 10I, i / 10I)) n
let consecutive = Seq.unfold (function
    (a : BigInteger) :: (b :: c :: d :: e :: _ as t) –>
        Some((a * b * c * d * e), t)
    | _ -> None)
73167176531330624919225119674426574742355349194934 ⏎
96983520312774506326239578318016984801869478851843 ⏎
85861560789112949495459501737958331952853208805511 ⏎
12540698747158523863050715693290963295227443043557 ⏎
66896648950445244523161731856403098711121722383113 ⏎
62229893423380308135336276614282806444486645238749 ⏎
30358907296290491560440772390713810515859307960866 ⏎
70172427121883998797908792274921901699720888093776 ⏎
65727333001053367881220235421809751254540594752243 ⏎
52584907711670556013604839586446706324415722155397 ⏎
53697817977846174064955149290862569321978468622482 ⏎
83972241375657056057490261407972968652414535100474 ⏎
82166370484403199890008895243450658541227588666881 ⏎
16427171479924442928230863465674813919123162824586 ⏎
17866458359124566529476545682848912883142607690042 ⏎
24219022671055626321111109370544217506941658960408 ⏎
07198403850962455444362981230987879927244284909188 ⏎
84580156166097919133875499200524063689912560717606 ⏎
05886116467109405077541002256983155200055935729725 ⏎
71636269561882670428252483600823257530420752963450I
|> digits |> List.ofSeq |> consecutive |> Seq.max

Comments

• Anonymous
  September 15, 2010
  I like your solution, very idiomatic for F#.I have taken a different approach to solve the same problem, based on arrays.If you are curious, you can have a look here: stefanoricciardi.com/.../project-euler-problem-8-in-f
• Anonymous
  September 16, 2010
  @Stefano: Hey, very nice solution! Now I'm going back and looking at your solutions to the others (I won't peek at 9+ until I've done them :-) Some fun, these Euler problems, eh?