Feedback and Questions

This is a good idea. I recently added that feature to Killer Sudoku, so I will do the same for Sudoku

It is (was) documented under "Singles Chains"/ However your question does raise the further question of why I don't pick one and be consistent, so I'll do that now. Goes way way back to like 2006 or something when the Sudoku community was still naming things and different sets of people used different names. So going with "Simple Colouring"

Hi Alan
Grader working for me as of testing just now. Let me know if it stops and if there is any error message or symptom. Send the puzzle so I can check that as well.
Regards the "check solved cells" these are usually a result of a naked or hidden single which are described in the text box. I highlight the number when it goes big for easy spotting.

Hi Chris. Just tested this and can't see a fault. send another feedback or email me so I can reply personally. See if we can sort this out. Anyone else having this problem?

Passed your comment on.

Very eloquent and interesting feedback, many thanks.
My only experience of tournament Sudoku was quite a long time ago. I was briefly involved one year with the Daily Telegraph when they ran an annual competition. I was pretty downcast by the very easy puzzle they picked and couldn’t understand why they chose it. Wasn’t my pick. The competition became a speed contest, not a thoughtful one. I’m sure other contests are better.

What’s happened with the advanced strategies like colouring wasn’t driven by contests or published puzzles really. People on forums were just interested in edge case puzzles that were found to be much more difficult than the usual fare. Often these enthusiasts would go looking for them and then advance some theory. Unlike most other pattern puzzles Sudoku happens to be unusually rich – I like to think as rich as chess. Which is why I started and continued with the site. I would not get very far or have much to say about Hitori or Kakuro for example.

Much of the site is devoted to these quite abstract and complex strategies as they are mainly of interest to other puzzle software writers but there is no clear divide where pen and paper stops. Now there are some very clever people who swear they use advanced strategies on pen and paper puzzles and they certainly enjoy doing them, whatever help they really use. So there is a market for them. But don’t publish extremes in newspapers as they would frustrate most players. The diabolical needs to be quite hard though – the spectrum is wide. I think if you avoid notes you should can validly use inspiration and still crack tough puzzles.

I agree that some patterns are so hidden you are trial and erroring in your search for them. It is an open question of whether there are more transparent replacements. We’re certainly not at the end yet of guaranteeing all puzzles have a logical solution.

Does QB64 have linked lists? I find having pointers very helpful. For example placing all cells in rows, columns and boxes into the same structure is very helpful and avoids writing code specifically for a row, or a columns or a box. Then adding other constraints in (for variants) is relatively trivial. I had to do this quite early as I was asked to make Jigsaws soon after vanilla. Use bit arrays also. Need two bytes for 9 numbers sadly but worth it for candidate spreads.

Best of luck with your solver and let me know how you get on

Interesting puzzle!
Not sure how you get the 3s removed from G7/H7. I'm sure you're right though.
The solver really struggles with such large cages as the number of dog-legs gets beyond what I programmed so it might be giving up on this cage at certain points.

I might have fixed it
Refresh now [CRTL]+[F5], will say v 2.12
Many thanks for the reports, and I hope it works now
All the best
Andrew

Possibly when I was updating the page. How is it now?

I wouldn’t try and compare two close scores as anything very meaningful. They work best in aggregate and statistically but there is too much arbitrariness at that grade. So with the puzzle with the extra clue a naked single is found. This takes priority over everything else so everything takes one step more than the other puzzle (14 steps not 13). There is weighting for how long a puzzle takes to solve/collapse which modifies the scores each round. That will bias the 14 step solution and give a slightly higher score.