Figlet-based CAPTCHA breaker (for IRC bots) -- accelerated!

unfiglet-dorei-slow.rb

require 'epitools'

figlet_left = File.readlines('./figlet.input')

def get_first_char(i, arr)
  arr.map { |x| x[0..i] }
end

def remove_first_char(i, arr)
  arr.map { |x| x.slice(i..-1) }
end

def find_figlet(arr)
  'A'.upto('Z').detect do |l|
    `figlet -f big -w 11 #{l}`.split("\n").reject {|x| x.strip.empty?} == arr
  end
end

time {
  res = '' 

  while !figlet_left.map(&:strip).reject(&:empty?).empty? do 
    i = 5
    while !(x = find_figlet(get_first_char(i, figlet_left))) do 
      i += 1
      abort("Partial result:#{res}") if i > 9
    end
    figlet_left = remove_first_char(i + 1, figlet_left)
    res << x
  end

  puts res
}

unfiglet-epi-fast.rb

require 'epitools'
require 'digest/sha1'

def hash_fig(arr)
  Digest::SHA1.hexdigest(arr.join("\n"))
end

def columnize(arr)
  arr.map(&:chars).transpose
end

ALPHABET = [*'A'..'Z']
FIGS     = `figlet -f big -w 11 "#{ALPHABET.join("\n")}"`.split("\n").each_slice(8).map { |fig| columnize(fig[0..5]) }
LUT      = Hash[ FIGS.map {|fig| hash_fig(fig) }.zip(ALPHABET) ]

figlet = columnize(File.readlines('figlet.input'))

time { 
  result = ""
  pos    = 5

  until figlet.empty? or pos > figlet.size
    hash = hash_fig(figlet[0...pos])

    if x = LUT[hash]
      result << x
      figlet = figlet[pos..-1] # drop the letter
      pos = 5
    else
      pos += 1
    end
  end

  puts result
}

$ ruby unfiglet-dorei-slow.rb 
LVUIJQ
elapsed time: 1.11940s

$ ruby unfiglet-epi-fast.rb 
LVUIJQ
elapsed time: 0.00059s

:D