palindrome_detector.rb

=begin

https://gist.github.com/drhuffman12/a5ad839b71e8ca334a2a

  Problem statement:

    Create a class named PalindromeDetector.  Within that class, implement a 
    static function named GetPalindromeYears that takes a start and end date as parameters and 
    returns a distinct set of Dates in chronological order(inclusive of start and end dates)
    that, when formatted as MMddyyyy, are palindromes.

    A palindrome is a string that reads the same forwards and backwards,
    for example: Nov 2, 2011 (11022011). You may add additional methods
    to this class if you choose, however this method's signature should
    remain unmodified.

  Example Usage:

    In code:

      start_date_str = 'Nov 2, 2001'
      end_date_str = 'Nov 2, 2014'
      PalindromeDetector.palindrome_years(start_date_str, end_date_str) #=> ["01022010", "11022011"]

    Via Command line:

      ruby palindrome_detector.rb "Nov 2, 2001" "Nov 2, 2014" #=> Palindrome Dates from 'Nov 2, 2001' to 'Nov 2, 2014' are: ["01022010", "11022011"]

=end

require 'date'

class PalindromeDetector
  
  def self.palindrome_years(start_date_str, end_date_str)
    start_date = Date.parse(start_date_str)
    end_date = Date.parse(end_date_str)
    palindromes = []
    (start_date..end_date).each do |_date|
      _date_formatted = _date.strftime('%m%d%Y')
      palindromes << _date_formatted if _date_formatted == _date_formatted.reverse
    end
    palindromes
  end
  
  def self.GetPalindromeYears(start_date_str, end_date_str) # Java method name syntax, since this came from a Java context.
    palindrome_years(start_date_str, end_date_str)
  end
  
end

if __FILE__ == $0
  start_date_str = ARGV[0]
  end_date_str = ARGV[1]
  palindromes = PalindromeDetector.palindrome_years(start_date_str, end_date_str)
  puts "Palindrome Dates from '#{start_date_str}' to '#{end_date_str}' are: #{palindromes.inspect}"
end