unfiglet-epi-opt-2.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_OPT = `figlet -f big -w 11 "#{ALPHABET.join("\n")}"`.split("\n").each_slice(8).map { |fig| columnize([fig[0], fig[2], fig[5]]) }
LUT      = Hash[ FIGS_OPT.map {|fig| hash_fig([fig[0], fig[2], fig[5]]) }.zip(ALPHABET) ]
SIZES    = Hash[ ALPHABET.zip(FIGS_OPT.map(&:size)) ]

figlet = File.readlines('figlet.input').map{|x| x.gsub("\n", '')}

def match_figlet(figlet)
  figlet = columnize([figlet[0], figlet[2], figlet[5]])
  result = ""

  until figlet.empty?
    hash = hash_fig([figlet[0], figlet[2], figlet[5]])

    if x = LUT[hash]
      result << x
      figlet = figlet[SIZES[x]..-1] # drop the letter
    else
      abort('SHIT')
    end
  end
  result
end
time { puts match_figlet(figlet) }

VERIFY = `figlet -f big -w 11 "#{ALPHABET.join("\n")}"`.split("\n").each_slice(8)

time { VERIFY.each { |f| puts match_figlet(f) } }

$ ruby unfiglet-epi-opt-2.rb 
LVUIJQ
elapsed time: 0.00014s
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
elapsed time: 0.00098s