worlds_shortest_sudoku_solver_refactored.rb

#  From
#
#  $*.map{|a|(i=a=~/0/)?(v=*?1..?9).fill{|j|v-=[a[j+i-k=i%9],a[
#  k+j*=9],a[j%26+i-i%3-i%27+k]]}+v.map{|k|$*.<<$`<<k<<$'}:p(a)}
#
#
#  To
start = Time.now
ARGV.map do |board|

  if index_of_zero = (board =~ /0/)
    buffer = (possibilities = ('1'..'9').to_a ).fill do |step|
      possibilities -=[ 
            board[step + index_of_zero - index_within_row = index_of_zero % 9],                           #row
            board[index_within_row + step *= 9],                                                          #col
            board[step % 26 + index_of_zero - index_of_zero % 3 - index_of_zero % 27 + index_within_row ] #box
          ]
    end

    steps_to_expand_from = possibilities.map do |possibility|
      ARGV.<< $` << possibility << $'
    end

    buffer + steps_to_expand_from
  else #if solved
    puts board
  end
end
puts "Solved in #{(Time.now - start).round(3)} seconds"