Result

 $ ruby queens.rb
 0 4 7 5 2 6 1 3
 0 5 7 2 6 3 1 4
 0 6 3 5 7 1 4 2
 0 6 4 7 1 3 5 2
 1 3 5 7 2 0 6 4
 1 4 6 0 2 7 5 3
 1 4 6 3 0 7 5 2
 ...