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Contents
defmodule Series do
@spec digits(String.t()) :: [non_neg_integer]
defp digits("") do
[]
end
defp digits(number_string) do
String.split(number_string, "", trim: true)
|> Enum.reduce([], fn char, acc -> [String.to_integer(char) | acc] end)
|> Enum.reverse()
end
@spec slices(String.t(), non_neg_integer) :: [list(non_neg_integer)]
defp slices(number_string, size) do
digits = digits(number_string)
chunk(digits, size, 1)
end
@doc """
Finds the largest product of a given number of consecutive numbers in a given string of numbers.
"""
@spec largest_product(String.t(), non_neg_integer) :: non_neg_integer
def largest_product(_, 0) do
1
end
def largest_product(number_string, size) do
unless Enum.member?(Range.new(0, String.length(number_string)), size) do
raise ArgumentError
end
slices = slices(number_string, size)
Enum.map(slices, &Enum.reduce(&1, fn x, acc -> x * acc end))
|> Enum.max()
end
# Handle Enum.chunks -> Enum.chunk renaming.
if {:chunk, 3} not in Enum.__info__(:functions) do
defp chunk(coll, n, step), do: Enum.chunks(coll, n, step)
else
defp chunk(coll, n, step), do: Enum.chunk(coll, n, step)
end
end
Version data entries
32 entries across 32 versions & 1 rubygems