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 email@example.com.
Post a Comment or Question here...
Thank-you everyone for all your questions and contributions.
... 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.
... 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.
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.
... by: Kate, London, UKLoad Sudoku X: CLICK TO LOAD
This 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.
... by: kenton, Alexandria, VA, USALoad Sudoku: CLICK TO LOAD
... 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.
... 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. :-)
... 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.
... by: JCS, Belgium
Share and Enjoy
... by: Tommy b, Scotland
... by: Ballooh, South Africa