Largest 5 digit number in a series

five-digit-max.rb

def solution(digits)
  group_by_five(digits).max
end
def group_by_five(digits)
  digits.split("")[0..-5].map.with_index do |digit, i|
    "#{digit}#{digits[i+1]}#{digits[i+2]}#{digits[i+3]}#{digits[i+4]}"
  end
end