kryptos.rb

#!/usr/bin/env ruby

# usage: echo <string> | ruby kryptos.rb
# assumes you have a spreadsheet or something open
# with the top left character (space) at column A, row 1

k4 = <<EOF.chomp.lines.map(&:chomp)
                           OBKR
UOXOGHULBSOLIFBBWFLRVQQPRNGKSSO
TWTQSJQSSEKZZWATJKLUDIAWINFBNYP
VTTMZFPKWGDKZXTJCDIGKUHUAUEKCAR
EOF

search = STDIN.read.strip.upcase

def search haystack, needle
  max_x, max_y = haystack.first.length - 1, haystack.length - 1
  haystack.each_with_index do |line, y|
    line.chars.each_with_index do |char, x|
      next unless needle[0] == haystack[y][x]

      pairs = [
        [x-1, y-1], [x-1, y], [x-1, y+1],
        [x, y-1], [x, y], [x, y+1],
        [x+1, y-1], [x+1, y], [x+1, y+1]
      ]

      pairs.each do |(xx, yy)|
        next if xx < 0 or xx > max_x or yy < 0 or yy > max_y
        if needle[1] == haystack[yy][xx]
          yield [x, y], [xx, yy]
        end
      end
    end
  end
end

def n2l n
  %w[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 AA AB AC AD AE AF AG AH][n]
end

matches, pairs = 0, 0
search.chars.each_cons(2).map do |pair|
  pair = pair.join
  matched = false
  search k4, pair do |(x, y), (xx, yy)|
    puts "#{matched ? '  => ' : ''}#{pair}\t#{n2l(x)}#{y+1}, #{n2l(xx)}#{yy+1}"
    matches += 1 if !matched
    matched = true
  end
  pairs += 1
end

puts "#{matches} unique match / #{pairs} pairs: #{'%.2f%%' % (matches.to_f / pairs.to_f * 100)}"