# 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. Please feel free to drop me a note on the side of the page or try the Facebook
comment box. Or you can email me directly at andrew@str8ts.com.
**Post a Comment or Question here...**
## Friday 24-Apr-2015

## ... by: Joe, Massachusetts

## Wednesday 15-Apr-2015

## ... by: unknown, far away

I'm totally new to this site, so please excuse me if this message is not relevant.

The solver indicates that the board below has 1 solution, but when i press the step button several times, the solver comes up with the error

ooops, error on your board, after incorrectly placing numbers against sudoku rules

where on your site can i read why this error happens ??

thanks

----

There is a Sudoku board I would like you to look at

Click on this link:

http://www.sudokuwiki.org/sudoku.htm?bd=009040500010503060400290007020000103003010000190600048501007002200300700070120035

Did you change the numbers manually at any stage?

"ooops, error on your board" suggests that, and it should highlight in red the conflicting cells

Andrew

## Friday 10-Apr-2015

## ... by: sundaresan, india

WELL, THIS IS WONDERFUL.a complete one. I thankyou for the amazing guide opens all the doors. I donot think no more tips and tricks around.

thank you friend

sundaresan

## Wednesday 8-Apr-2015

## ... by: LWNK, USA

## Saturday 28-Feb-2015

## ... by: Dale E. Kloss, Portland, Oregon, USA

Is that true? it seems likely but I have always wondered.

This seems to be related to finding a U.R. exemplar.

Thanks. Dale Kloss

## Tuesday 24-Feb-2015

## ... by: Chuck, Virginia

Load Sudoku: CLICK TO LOADI have 2 questions. The first concerns the X-Cycles (Part 2) description. The third paragraph has a line that reads "Discontinuity' doesn't mean that the loop is broken or that it's a chain." Am I incorrect in thinking that it should read "Discontinuity' doesn't mean that the loop is broken or that it's NOT a chain"?

My second question concerns the Sudoku that I have included. If you select only the X-Cycle strategy and then step through the puzzle until it stops on the X-Cycle, everything looks good. Now, do a back step, deselect the X-Cycle, select Grouped X-Cycle, and do a step. The solver stops with the exact display as before, but the description at the bottom states that it found a Grouped X-Cycle. Is this a mistake in the solver?

Thanks for taking the time to look at this. I love your site and recommend it to all my friends and acquaintances that are in to Sudoku.

Chuck Bruno

Grouped X-Cycles includes all X-Cycles so yes if you turn the first off then a normal X-Cycle will turn up in the grouped one. I suppose I could filter them but what I am doing is performing a search with additional flags (yes to grouped cells and other types of links) rather than negatively filtering the first. Grouped X-Cycles is a super set of X-Cycles

## Wednesday 18-Feb-2015

## ... by: Mark, Australia

Thank you for creating and maintaining this website. Being shown how to solve a given puzzle, step by step, is wonderfully educational! In just a few minutes, with your step-by-step solver, I have learned more than I'd learned in hours, poring over static examples at other websites. Thank you for freely sharing this functionality!

Cheers.

Mark

## Saturday 14-Feb-2015

## ... by: FallsOffRocks, UK

Surely Rule 4 is just a constrained subset of Rule 5, with the constraint being that the two coloured candidates that the candidate to be eliminated can see must be in the same unit as the candidate to be eliminated?

I cannot really see a separate justification for rule 4.

LOAD PUZZLE

This one had 2x Rules 4 and 2x Rules 5 3D Medusas, but I'm patching the solver tonight, so you wont see them unless yr quick. It now shortens the solution path.

LOAD PUZZLE

This puzzle has many Simple Colorings - only the last right at the end does the new rule get two 4s instead of one.

Basically, all I need to do is remove the code for Rule 4 and let Rule 5 do the job. That's awkward because I now have to rename Rule 5 to Rule 4 and Rule 6 to Rule 5. Can't have a gap in the sequence. I'll try to update the documentation on Simple Colouring and 3D Medusa at the same time.

I'd be delighted to credit you on the pages.

It's rare to find a simplification, it's normally the case I have to add a complication

## Friday 13-Feb-2015

## ... by: FallsOffRocks, UK

I was validating my own solver and loaded up your Y-Wing example. My own Y-Wing algorithm clearly scans in a different sequence from yours, as it showed up a completely different Y-Wing, a very nasty one to spot without assistance. Just rotate the puzzle and your solver gets the nasty one first.

Now I have to start on the chaining methods :(

Ideally I'd like to give the user an option to scroll through all the instances of a given strategy but it would greatly complicate the UI.

## Monday 9-Feb-2015

## ... by: 0t0, europe

Load Sudoku: CLICK TO LOAD4..9..8...3..6..4...1..8..51..7.......3.4.2.......1..82..8..5...5..9..2...7..3..9

My first 3D Medusa Sudoku!