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Contents
# see also https://gist.github.com/blairand/5237976
# see also https://gist.github.com/burtlo/89b0b817fdccf6bdf20f
module BookKeeping
VERSION = 3
end
class Series
attr_reader :digits
def initialize(numeric_string)
@digits = numeric_string
end
def largest_product(length)
@length = length
validate_length
return 1 if @digits.empty?
collection_of_digits
select_max { reduce_to_product { validate { separate } } }
end
private
def validate_length
@length < 0 and
fail(ArgumentError.new 'Length must be non-negative')
@length > digits.length and
fail(ArgumentError.new 'Not enough digits')
end
def validate
yield.take_while { |array| array.size == @length }
end
def reduce_to_product
yield.map { |array| array.inject(1, :*) }
end
def select_max
yield.max
end
def separate
digits.map.with_index do |_, index|
digits[index, @length]
end
end
def collection_of_digits
@digits !~ /^\d*$/ and
fail(ArgumentError.new 'String must contain only digits')
@digits = digits.chars.map(&:to_i)
end
end
Version data entries
239 entries across 239 versions & 1 rubygems