[HugoDias]

A solution for doing the same thing in Ruby: https://gist.github.com/hugodias/cf89ba138b986ddb3e7d

Time spent processing for 12 queens: 3.59 seconds

[tacticiankerala]

Here is the benchmarking for 12-queens

12-queens : 0.21s user 0.11s system 129% cpu 0.244 total

But, I see that you are finding all the solution. My program only finds the first solution.