Largest 5 digit number in a series

=begin
Largest 5 digit number in a series

link: http://www.codewars.com/kata/largest-5-digit-number-in-a-series/

description:
In the following 6 digit number:
283910
91 is the greatest sequence of 2 digits.
Complete the solution so that it returns the largest five digit number found within the number given.. The number will be passed in as a string of only digits. It should return a five digit integer. The number passed may be as large as 1000 digits.

=end

#my version
def solution(digits)
  str = digits.to_s
  maxsum_str = ""
  for index in 0...str.length-4
    sum = "#{str[index]}#{str[index+1]}#{str[index+2]}#{str[index+3]}#{str[index+4]}"
    if( sum.to_i > maxsum_str.to_i )
      maxsum_str = sum
    end
    if( sum.to_i==99999 )
      return maxsum_str.to_i
    end
  end

  return maxsum_str.to_i

end

#best practices #1
def solution(digits)
  digits.split('').each_cons(5).max.join.to_i
end

#best practices #2
def solution(digits)
  digits.scan(/\d{5}/).max.to_i
end