Solver App for Android
Strategies for Popular Number Puzzles
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Feedback and Questions

I've received a lot of interesting comments and questions from Sudoku fans over the last few years and this page is where I try to answer them. I'm also directing Str8ts feedback here. Please feel free to drop me a note on the side of the page. Or you can email me directly at .

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Any Sudoku you want to publish here for easy loading into the solver - 81 characters, use '.' or '0' for unknowns.

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Many thanks to all the people who have helped improve the solvers and strategies with their feedback!

Friday 17-May-2024

... by: blortch1, Hawaii

I suggest moving APE into the Extreme Strategies section. APE appears to require a computer - unless one has an unlimited amount of time in their life - to detect where it could be used.

Andrew Stuart writes:
Might swap with Grouped X-Cycles but then no APE might appear. Will have to do quite a bit of testing but I understand your assessment

Tuesday 16-Apr-2024

... by: Aubrey de Grey, United States

I'm finding that I can't turn off Death Blossom - puzzles use it even when it's unticked. I've seen this three times now - I don't think it's a refresh issue.

Andrew Stuart writes:
Yes this was a feature rather than a bug. When I look for the previous strategy "Almost Locked Sets" I get a "Death Blossom" result for free. However I can see that is confusing with the checkboxes so I now null the result if DB is checked off

Saturday 6-Apr-2024

... by: ,

I opened the SudokuSolver app on my Android tablet. When I chose Daily Puzzles, the app just hung at downloading today's puzzles (for April 5). I couldn't back out; the only option was to close the app. I tried a few times. Same result. I restarted the tablet. Same result. I went to the Google Play Store in case there was a new version. Nope. I am up to date.

Andrew Stuart writes:
Working for me, just tested now. Version 1.85. Can you get back in contact with an email address. Try and figure this out

Thursday 28-Mar-2024

... by: Dr John Collins, Australia

Whenever I enter a new kenken I never get a clear box for the solution. It always leaves a solution so I have to remove each digit in the solution for each of the 36 entries.

Andrew Stuart writes:
I will add a button. Good idea

Thursday 28-Mar-2024

... by: Link, USA

I'm writing a solver in Python. I could benefit from a feature on your site that downloads (or displays a copy-able string) of the 81 character array from your puzzles. This would help me greatly in testing.
Thanks. Link Reynolds

Andrew Stuart writes:
If you use the [Email this board] button you get two strings, the 81 char and the longer one with candidates
Or do you want something more API-ish?

Thursday 28-Mar-2024

... by: Matthew L, USA

Load Sudoku:

I think I've found a bug, or I simply cannot understand the step suggested in the solver from a "strong link" between 2 on H9 and the group of 8s on H2&H9. Here is the solution from the solver:

Alternating Infer. Chains
AIC on 8 ((w.Groups) Discontinuous Alternating Nice Loop, length 10):
- Contradiction: When F2 is set to 8 the chain implies it cannot be 8 - it can be removed

Andrew Stuart writes:
That is a Naked Pair chain link. By removing the 2 in H9 you get a pair in H2 and H9 on 5 and 8. One exit from the Naked Pair is -8[H1]

Saturday 16-Mar-2024

... by: Chris B, Canada

I noticed today that the Ipad and Iphone buttons are missing from the Daily Sudoku (present for Str8ts). Is that intentional? Thanks!

Andrew Stuart writes:
Still there, just scroll down a bit more, under the player

Monday 4-Mar-2024

... by: Jan, Den,ark

First thank you for this amazing sudoku-solver!
Is it possible to type in the shape of the jigsaw sudoku? The site has a limited number of predefined shapes that does’nt match my jigsaw for which I need help. I imagine that I type 1 to 9 repeating the same number identifying each box shape.

Andrew Stuart writes:
Almost top of my job list. I need a way of getting the shapes into the server side solver. But certainly possible I'm sure

Wednesday 28-Feb-2024

... by: World, USA

Load Sudoku:

Not sure if this is a bug but using your solver on this sudoku produces a peculiar result. When you get to the hidden triple in Box 7 (126) and Column 1 (156), the Box 7 hidden triple eliminates 5 from J1 but then the 5 is added back since it is part of the hidden triple in Column 1.

Andrew Stuart writes:
I think you might have stumbled across something funny going on there. The solver allows all hidden pairs and triples to apply in one step but long ago I wrote the code to not implement the eliminations until after all were assessed. This is to avoid cascading effects which would be hard to trace. However in this instance part of a hidden triple was a number which was previously flagged as eliminated - but not invalidating the following triple. I've changed it now to preserve the elimination in this case. Subtle and rare but nice to get

Thursday 22-Feb-2024

... by: Peter O, Germany

A super website

Andrew Stuart writes:
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Thank-you everyone for all your questions and contributions.