Show HN: NQueens problem solved using backtracking in Elixir lang

https://github.com/tacticiankerala/N-Queens

19 7 11 years ago

taeric3• 11 years ago

It would be interesting to see timing results of this implementation. Similarly, comparisons to other implementations/algorithms. I will have to fire up erlang when I get home this evening.

I am basically a broken record on this topic, but I do like sending more people to see the Dancing Links algorithms solving this (and other related problems, such as sudoku.)[1] The techniques in DLX cut the search space for the 8-queens down to just 1,048 board states. (For 13, the number of boards is up to 1,046,318)

[1] http://taeric.github.io/DancingLinks.html

tacticiankerala3• 11 years ago

8-queens : 0.19s user 0.09s system 127% cpu 0.222 total

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

16-queens : 0.29s user 0.10s system 119% cpu 0.325 total

20-queens : 2.79s user 0.10s system 102% cpu 2.826 total

24-queens : 7.50s user 0.10s system 100% cpu 7.533 total

Thanks a lot for sharing the Dancing links algorithm. It looks really interesting. I wanted to try sudoku with backtracking,but now I would like to give dancing link a try!

taeric3• 11 years ago

Are those times for finding a solution, or for all solutions? If all, that is truly impressive!

Dancing links is a backtracking algorithm, just a nice way to optimize the backtracking.

HugoDias• 11 years ago

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

Time spent processing for 12 queens: 3.59 seconds

tacticiankerala3• 11 years ago

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.

Show HN: NQueens problem solved using backtracking in Elixir lang

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