Euler Solution 8

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Solutions for Problem 8

Find the greatest product of five consecutive digits in the 1000-digit number shown below.

Ruby by tomchristmas

Runtime: 17ms

str = "73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450"

product = 0
multiplicands = ""

(str.length - 4).times{|x|
    p = str[x,1].to_i * str[x+1,1].to_i * str[x+2,1].to_i * str[x+3,1].to_i * str[x+4,1].to_i
    if p > product
       product = p
       multiplicands = "#{str[x,1]} x #{str[x+1,1]} x #{str[x+2,1]} x #{str[x+3,1]} x #{str[x+4,1]}"
    end
}

puts "#{product} = #{multiplicands}"

Caml by SanguineV

Runtime: 11.66 ms

(* WARNING: this code generates a compile warning and will cause an exception if
 * the "maxmult" function is called on a string that containts any characters not
 * in the range '0'-'9'! *)

let thenum = "..." (* Left out for brevity of solution (sort of) *)

(* A long and complex function, partly because I chose to do as much as possible
 * in the function and limit calls outside of this code. *)
let maxmult str =
  (* Define a local function to convert characters to ints using pattern matching *)
  let charvals = function
    | '0' -> 0
    | '1' -> 1
    | '2' -> 2
    | '3' -> 3
    | '4' -> 4
    | '5' -> 5
    | '6' -> 6
    | '7' -> 7
    | '8' -> 8
    | '9' -> 9
  in
  (* A list for the "group" of numbers to multiple, using a list to do more
   * functional programming and not imperative style loops! The numbers in the
   * group represent the offset from a position for the other characters/digits
   * to multiple. *)
  let group = [0;1;2;3;4] in
  (* Inner recursive function to go through the string. "i" is the current index
   * in the string. *)
  let rec inner i =
    (* Reached the end of the string. *)
    if (i + 5) <= String.length str
    (* The "fun" part, fold the multiplication over the map of the group to
     * the ints that represent the characters in the string. Add the result to the
     * head of a list of ints and continue. *)
    then (List.fold_left
      (fun x y -> x * y) 1
      (List.map
        (fun x -> charvals
        (String.get str (x + i))) group))
      :: (inner (i + 1))
    else []
  in
(* Fold a function to find the maximum over the list of results generate by
 * the "inner" function. *)
List.fold_left max 0 (inner 0)
;;

(* Print the result of finding the maximum multiplication of "thenum"! *)
Printf.printf "Max result is: %u\n" (maxmult thenum);;

Python by Althalus

Runtime: 19 ms

from math import sqrt
import time

start_time = time.time()

numbers = "73167176531330624919225119674426574742355349194934\
96983520312774506326239578318016984801869478851843\
85861560789112949495459501737958331952853208805511\
12540698747158523863050715693290963295227443043557\
66896648950445244523161731856403098711121722383113\
62229893423380308135336276614282806444486645238749\
30358907296290491560440772390713810515859307960866\
70172427121883998797908792274921901699720888093776\
65727333001053367881220235421809751254540594752243\
52584907711670556013604839586446706324415722155397\
53697817977846174064955149290862569321978468622482\
83972241375657056057490261407972968652414535100474\
82166370484403199890008895243450658541227588666881\
16427171479924442928230863465674813919123162824586\
17866458359124566529476545682848912883142607690042\
24219022671055626321111109370544217506941658960408\
07198403850962455444362981230987879927244284909188\
84580156166097919133875499200524063689912560717606\
05886116467109405077541002256983155200055935729725\
71636269561882670428252483600823257530420752963450"

#number_list = numbers.split()

i=0
biggest_mult=0

while i+5 <= len(numbers):
	temp_result = int(numbers[i])*int(numbers[i+1])*int(numbers[i+2])*int(numbers[i+3])*int(numbers[i+4])

	if temp_result > biggest_mult:
		biggest_mult = temp_result
	i+=1 

print(biggest_mult)
run_time = time.time() - start_time
print (run_time)
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