Feedback and Questions

The sudoku solver may be saved to your computer to use when you are not connected to the internet. However, without internet access, it will only perform the basic strategies 1 through 7, because the more difficult strategies execute on a server accessed via the internet.

To save the solver, in Internet Explorer, click File on the Menu Bar. (If the Menu Bar is not displayed, press the Alt key.) Click Save as. Change the type to Webpage complete and navigate to the folder where you want to save the solver. Click the Save button. The default name for the solver is Sudoku Solver by Andrew Stuart.

To use the solver while not connected to the internet, launch the solver from the saved location. Enter your puzzle the normal way, then press the "Take Step" button. If you get a No on step 7: Box/Line Reduction, do not press "Take Step" again. Save the puzzle by pressing the Save button. You must now solve at least one of the squares on your own, using advanced strategies, or just enter one of the candidates.

If you just enter a candidate, make a note of the number you chose. If you pick a wrong candidate and the solver later tells you that you have a error on the board, click Re-Load and try the other candidate.

If you just choose a candidate, to speed things up, try to choose a square with two candidates. Then, if you enter the wrong candidate, you have only one other candidate to try later.

More difficult puzzles may require entering candidates in two or three squares. When you get a second No to step 7, enter a candidate in another square and Take Step again.

I shouldn't be using 'square' anywhere - it’s probably down to a drift in the text as it was developed over several years. I'll keep an eye out and change those

Thanks for the alert

Thanks for the alert, fixed that. Appreciated

This is an interesting question and to explore it fully I've created a new article. Have a look at this:

The Relative Incidence of Sudoku Strategies

That's an awesome use of some difficult tech. My backend to this site is SQL server so I know stored procedures are not the easiest things to create. Hat's off to you :)

Reason I don’t use Chrome when using my solver is that the "Enter" key does not work on the "Take Step" button. In other browsers once you click on it its the default button for "Enter". So I have to click and it takes longer. However, I can't find any other your other problems. Results pane clears when new data is loaded. Steps are in sequence. Just installed it, version 3.0.195.32

All chains, infact all strategies that have a tick beside them, do only report the first successful occurrence of that strategy. There shouldn't be several at once. I agree that what would be nice is to show with lines the connections between the cells. Currently I only highlight the cells being used. This is a bit of a technical challenge though, given the medium.

If by more than one chain - you mean lots of dead ends and branches, yes that is the nature of the beast.

I was aware there were interesting combinations and if you have examples I'd be interested to code them and add them to the solver. If they are original I'd certainly like to add a credit to yourself or a pointer to the source. I know it often the case these ideas just bubble up from the community in general. From an example I can generalise an algorithm. Usually with a new approach I'd test it against a huge library and see how it contributes to reducing the solve path (and therefore the difficulty of the puzzle). Be happy to share the results with you.

I don't get your error. I loaded the Sudoku and pressed "take step" until it finished. No hard strategies required. Solution count = 1 solution. I don't know how you generated the problem.

+----------------+--------------+--------------+
|    29   7    6 |   59  25   1 |    3  48  48 |
|    13   8    4 |   36   7 369 |   19   2   5 |
|   123  35 2359 |   23   4   8 |    7   6  19 |
+----------------+--------------+--------------+
|     5  13   38 |    7   6   2 |   89  14  49 |
|     6  19    7 |   59   8   4 |    2  15   3 |
|     4   2   89 |    1   3  59 |    6  58   7 |
+----------------+--------------+--------------+
|    28   6   35 |    4   9  35 |   18   7 128 |
|  2378   4   23 |  236   1 367 |    5   9 268 |
|   279  59    1 |    8  25 567 |    4   3  26 |
+----------------+--------------+--------------+

I stepped through to the position below. I don't see how you eliminated the 2 in G3 to make the x-wing. My next step would have removed

SINGLES CHAIN (Type 1): Removing 2 from H1

Making it beyond your board above