N-queens puzzle

#!/usr/bin/env ruby

def print_board(board)
  board.each do |row|
    row.each do |i|
      print (i ? "x" : ".")
    end
    puts
  end
  puts
  1
end

def queens(b, c, l, r, k, n)
  if k == n
    print_board(b)
  else
    count = 0
    n.times do |i|
      unless c[i] or l[k+i+1] or r[i-k+1]
        b[i][k] = c[i] = l[k+i+1] = r[i-k+1] = true
        count += queens(b, c, l, r, k+1, n)
        b[i][k] = c[i] = l[k+i+1] = r[i-k+1] = false
      end
    end
    count
  end
end

n = if ARGV.length == 0
  print "Podaj wielkosc planszy (domyslnie 8): "
  ((line = gets).strip != "" ? line.to_i : 8)
else
  ARGV[0].to_i
end

r = queens(
       Array.new(n) { Array.new(n, false) },  # plansza
       Array.new(n, false),                   # kolumny
       Array.new(2*n, false),                 # lewa diagonala
       Array.new(2*n, false),                 # prawa diagonala
       0,                                     # postaw hetmana w pierwszej kolumnie
       n                                      # N kolumn
    )
puts "Rozwiazan: #{r}"