# 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...**

## Saturday 17-Aug-2013

## ... by: Ray, Iowa, USA

## Wednesday 7-Aug-2013

## ... by: LisaGreen, England

If a number has been solved and thus turns blue, taking a step back leaves the colouring as blue. This may be by design though Andrew.

Hugs

Lisa

Yeah, that's kind of a bug. Not a fatal one though! Will add to the job queue.

best regards

## Saturday 20-Jul-2013

## ... by: Wayne, California

Refresh the page (F5) a few times if the scipts are not updating

## Wednesday 3-Jul-2013

## ... by: Derrick T, UK

I hope you do not mind me emailing you directly about this but I did not want to put this on the Android site else people see it as a negative.

Please advise if its me doing it wrong.

Thank you

Kind regard

Derrick T

Can you go to the preferences page and tell me what it says at the bottom? That has the technical specs for your device and I can run a simulator with those settings and see how it looks.

On hint mode I was wondering about this. Currently it is binary and if ON then it will show

a) the strategy used

b) the green candidates which are used in the pattern to make the strategy work

c) any cell coloring

d) the lines used in Simple Coloring

it will not show

e) the eliminated candidates

f) any chains

What I wanted was some compromise between two much information and too little. I think you think there is still too much. It depends on the strategy, some will be a bit obvious. But giving people the chance to trace the eliminations from the minimal highlighted candidates seemed a good idea. I think I need to have a trinary hint mode. The current one and a very minimal which just states the strategy used.

I'll add that to the next update. Would that work for you?

## Monday 1-Jul-2013

## ... by: Prahas, USA

## Friday 21-Jun-2013

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

Is the puzzle pack partly Killer and partly Jigsaw but no Killer & Jigsaw combined in one puzzle? Or am I missing something about this website ? Is there a way to force one of the solvers to solve KILLER JIGSAW puzzles or am I being a dense dunce ? ;)

Dale Kloss

## Saturday 15-Jun-2013

## ... by: Jonathan Norris, London, UK

Many thanks!

Killer Cage Splitting

All the cages entirely inside columns 1,2 add up to 70. The cage starting on C1 can be split into an Innie (4 cells that sum to 20) and an Outie (2 cells that sum to 12). The new cages have combinations that mean...

we an remove 1/2/6 from A3

we an remove 1/2/6 from A4

## Tuesday 11-Jun-2013

## ... by: Flozoe11, Newport News, VA

## Sunday 9-Jun-2013

## ... by: Simon McCarthy, UK

First let me compliment you on an excellent website. I've often wondered how Sudoku puzzles are created and what the minimum number of clues to ensure a unique solution was - I haven't finished reading the proof of the latter, but I am finding it very interesting. Also, your killer Sudoku solver is a genius (and makes them all seem really easy, no matter how long I take using a pen and paper).

Anyway, I was curious to know whether you ever thought of an easy way to email and import Killer Sudoku? (It says on the notes that you wrote on your Killer Sudoku solver v1.02 that you were intending to come up with a method). I should point out, that I come from a mathematical background, rather than a programming one (so have some idea what this problem is about, but may not understand all of the intricacies).

Having said that, I reckon it must be possible to encode a Killer Sudoku (without using too long a string!) What's the maximum length the string is allowed to be? I reckon it's possible to describe any Killer Sudoku in any state of completion, using a string of 619 characters. Would that be too long?

Kind regards,

Simon McCarthy

Killers require the cages and the clue numbers. The grid, the box shapes and the size is assumed. In the early days I noticed a lot of definitions tried to use cage boundaries but this is overly complex. For me, it is sufficient to have a 'mapping color' (the classic 4 color mapping problem) and a cage boundary is merely where adjacency has two different colors. The mapping color algorithm is most visible in the cage drawing popup (see "Enter New Killer") but it very basic - I allow a fifth color if necessary (A sixth is available but I've never seen it). Internally cages are numbered so I can uniquely identify them and create more (cage splitting strategy eg) and the numbering could be used instead of the mapping color but the mapping color only requires one digit.

Clues are assumed to be placed in the top leftmost cell of any cage. The solver will barf if they are not. This leaves a lot of zeros. A string of numbers delimited by commas would be shorter but harder to debug/read manually. So the 'standard' email link I employ is 81+162 characters of data:

Click on this link:

http://www.sudokuwiki.org/killersudoku.htm?bd=1121222121221131321333231332314244442414122222

41333132233112131111322131224344431,14002117140000030700000000001

4052200001900001200000000270018150016000000000500000126000000000

0001300002219000011001000150000120900000700000000001300030015000

00000

Now, there is huge scope for compressing this but I haven’t researched it - something I've been meaning to do. I have noticed that some email systems refuse to turn this into a hyper link that includes all the data, which is annoying - and that’s the only reason I'd want to compress it.

I should also get on and do the import popup but I'm not sure how anyone else stores their killers electronically. Sudoku definitions abound (and are easy to import) but killer needs two different strings as input. I've assumed most people will be 'importing' through a link like the one above.

## Thursday 6-Jun-2013

## ... by: Stephen Carman, retired Electronic Technician

Load Sudoku: CLICK TO LOAD+2J8-8J8 +8H8-2H8 +2H3-5H3 +5j1 which is impossible given J4. If this chain is written correctly then how is it that I should interpret it's results? If it is written incorrectly then where did I go wrong?

+---------------+-----------------+--------------+

| 3 16 9 | 256 18 258 | 4 7 25 |

| 2 146 15 | 7 134 9 | 8 16 35 |

| 145 8 7 | 2456 134 235 | 9 126 235 |

+---------------+-----------------+--------------+

| 7 5 4 | 8 6 1 | 2 3 9 |

| 6 13 13 | 9 2 4 | 7 5 8 |

| 9 2 8 | 3 5 7 | 6 4 1 |

+---------------+-----------------+--------------+

| 148 1347 123 | 24 3478 238 | 5 9 6 |

| 458 49 25 | 1 489 6 | 3 28 7 |

| 58 379 6 | 25 3789 2358 | 1 28 4 |

+---------------+-----------------+--------------+

-5[h3] +5[j1]

In this case you can't turn off -5[h3] AND then ON +5[j1] because there is another 5 in H1. When you turn OFF and make a strong link there must be only two candidates left in the unit or cell. Weak links where you turn ON obliterates all other candidates in every direction from two upwards.

Hope that helps

## Friday 24-May-2013

## ... by: Robin Thornton, France

I have a problem concerning the Daily Killer for 23/5/2013 and I have spotted an error in your explanation for a step. However firstly I would like to complement you on your marvelous site and thank you for all the pleasure it has given me.

I was stuck in attempting to solve yesterday's Killer so I stepped through your solution and all went exactly according to my own progress until I reached the step in which you said that the 4's could be removed from A4 and A6 on the grounds that the valid combinations for a Cage of value 10 with 3 cells would not allow them. Here you gave the valid numbers adding up to 10 for a Cage of 3 cells in which you included 8 and 9 which are clearly not possible (the error). I cannot reproduce the puzzle so I can only refer to my own paper version. At this point I had possibles :-

A5 1,3,4,5

A6 1,3,4,5

B5 2,4,5,6

As there is no 1 in B5 it would be perfectly possible to have:

A5 1 A5 4

A6 4 or A6 1

B5 5 B5 5

Hence no reason to remove the 4's from A5 and A6?

As your Solver managed to solve the Killer your action must have been correct but for the life of me I cannot understand your reasoning.

Keep up the good work!

Regards,

Robin Thornton

I've also improved the text returned on cage combinations. I also spotted another bug where the last remaining cell in a cage wasn't being returned. A Bit of a howler that as it’s an easy thing to compute and a human would fill it doing it on pen a and pencil. But it is now showing on the solver. The check was in my offline solver which is probably why I didn't spot it before.

Solvers all say version 1.94 now, so refresh a few times if you don’t see that.