# 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 andrew@str8ts.com.
**Post a Comment or Question here...**
## Thursday 29-Dec-2011

## ... by: Bill, Florida

The problem is candidate density. If you look at my solver when it comes to 'Run out of known strategies' you will see most cells contain 3 or more candidates. Most of the advanced strategies and all the chaining ones require bi-value (2 in one cell) or bi-location (2 in one unit) to get anywhere. So there is plenty of room for more thought and ideas, which is the attraction of Sudoku – its very deep.

## Sunday 11-Dec-2011

## ... by: Hache, UK but living in France

Not sure whether this is a bug or not. I am using a MacBook Pro running Mac OS X and Safari. Pressing enter on the keyboard after 'take step' has no effect.

Also a question: Sometimes when I'm stepping through to check a solution I notice that although I have completed the grid correctly I haven't always arrived there by the same route as the solver. Does that mean that I have arrived at the correct solution by coincidence rather than true logic or are there multiple routes to solving a grid?

Fantastic site by the way - I use it every single day.

Many thanks

Yes there are many routes possible - unchecking some of my strategies will reveal alternatives, but even within a strategy it only returns the first or shortest example. I have tried to use logical and statistical techniques to order the strategies in terms of complexity and then return the easiest/shortest solve routes so I hope it is optimal, but humans also have intuition which I can't program. So you might find another way.

## Saturday 3-Dec-2011

## ... by: Kate, London, UK

Load Sudoku X: CLICK TO LOADThis is an X Solver: After a few steps you say that Simple Colouring Rule 5 removes candidate 7 in B2, because it can see two different coloured 7's elsewhere. But it can only see two greens - if the solution was a purple 7 how does it eliminate the 7 in B2? What am I missing?

This is a nice example of Simple Colouring in Sudoku X - short because of the diagonal. The 7 in B2 can see two green cells - and importantly the blue 7 in G9 because of the diagonal. This is an excellent example of taking advantage of thee extra constraint.

## Friday 2-Dec-2011

## ... by: kenton, Alexandria, VA, USA

Load Sudoku: CLICK TO LOAD## Tuesday 29-Nov-2011

## ... by: Lewy, Alaska, US

I'm sure that would be difficult to do, but it surely would be helpful.

And ... many thanks for all the work you have put into this page. Great job.

--Lewy

## Thursday 17-Nov-2011

## ... by: triemers, Netherlands

Today's Killer Sudoku has multiple solutions. Your solver (if you let it run unassisted) will only show one because of an assumption made regarding the possible combinations allowed in a cage: no number can ever occur twice within a cage. This however is not valid when the cage crosses Box boundaries.

Specifically for today A3-A4-B4-C4=21, your solver shows as solution (4,9,1,7), when (4,6,4,7) is also a valid combination in this puzzle. It will actually lead to multiple valid solutions.

BTW: I thoroughly enjoy my daily ration of puzzles. :-)

The_Killer_Cage_Convention

## Friday 4-Nov-2011

## ... by: Pete, cincinnati,oh,usa

guessed my way to an answer

loaded it into your solver said solution count zero

the solver solved it too a bunch of steps with the extreme chains

Daily Jigsaw Sudoku for 4-Nov-2011

No 96, Diabolical

There is a problem with the solution count on the jigsaw solver. Its not working for me but is working offline. I'll have to figure that out first.

## Saturday 29-Oct-2011

## ... by: JCS, Belgium

Share and Enjoy

## Friday 28-Oct-2011

## ... by: Tommy b, Scotland

## Wednesday 19-Oct-2011

## ... by: Ballooh, South Africa