SudoCue Users

Do you have a list of 18 clue minimal puzzles that you would share?

There is so much attention on 17s, yet there should be about 3 million 18s.

Anyone have a list of some?

I have seen a list of about 100, there are for sure way more.

Gordon F Royle had a list of 18 clue sudokus on his website, but took it down, probably because it cost him a lot of bandwidth to have such a large file available for download.

There is a relatively easy way to create a large series of 18 clue sudokus:

For each 17-clue sudoku in Gordon's collection:

remove 1 clue at random, then add 2 clues at random. Check for a unique solution and whether the puzzle is minimal. If it is not, you might be able to find a new 17, but this is highly unlikely, because several people have already performed an exhaustive "remove 1-add 1" search on the collection.

Thanks Ruud!

If you have a look over at the Players Forum you'll find an ongoing discussion about 17/18 clue puzzles under General/Puzzles. Gordon Royle and others are posting info on that forum so you can fill in a bit more on the techniques that Ruud mentioned and the latest findings.