[201607-ABCTF] TGIF Solution

tgif-solve.rb

<<META
  Contest: ABCTF
  Author : Rei_Fan49
  Team   : WhiteHat
  Date   : 2016/07/15
META

# STL
require 'date'

# Basic framework
END {
  err = 0
  begin
    main(*ARGV)
  rescue Interrupt => it
    err = 2
  rescue Exception => ex
    STDERR.puts([ex.class,ex.message].select{|x|(x.to_s).length>0}.compact * ': ')
    STDERR.puts(ex.backtrace * $/)
    err = 1
  ensure
    exit(err)
  end
}

# Main Program
def main(*argv)
<<-SOLVEDOC
  To solve this via ruby, it might be simple, but the actual flag isn't what you expected.
  1. Load the file and read all the lines into array buffer
  2. Parse with Date STL that Ruby have
  3. Shift the date 12 months ahead.
  
  You get the number, how about the flag?
  
  Well, as the instruction is simply to wrap with "abctf{(.+)}".
  But there's something strange, if you just only submit the number,
  let's say "abctf{123}". The grader will treat it as wrong thing.
  Since the context is friday, how about we append 'friday' on the answer?
  Something like "abctf{242fridays}" or something.'
  
  Yeah, it kinda surprised me that the grader accepts that kind of answer.
  (Of course it's 194 dude.)
SOLVEDOC
  
  File.open('data.txt','r'){|f|
    ary = f.readlines
    ary.map!{ |d| Date.parse(d) }
    ary.map! { |d|
      nd = d << (-12)
      # This will spam your STDOUT for sure
      puts "#{d} #{d.friday?} => #{nd} #{nd.friday?}"
      nd
    }
    puts ary.select{ |d| d.friday? }.length
  }
end