#### Description

From Project Euler: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

#### Solution

This problem is another one that is very easy to brute force, especially since Ruby has some nice built-in methods that make it a no brainer. One thing we will need is an easy way to take a number and break it up into it’s digits. For that a simple method added to the Integer class will do.class Integer def digits self.to_s.split('').map { |s| s.to_i } end end

The first thing we need to find is all the combinations of 5 consecutive digits. We can make use of the Enumerable#each_cons method to accomplish this.

class Problem008 def partition(number) number.digits.each_cons(5) end end

class Problem008 def products(number) partition(number).map { |a| a.reduce(1, :*) } end end

THOUSAND_DIGIT_NUM = # number from problem statement products(THOUSAND_DIGIT_NUM).max # This could have been written all in one line as THOUSAND_DIGIT_NUM.digits.each_cons(5).map { |a| a.reduce(1, :*) }.max

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