Feedback and Questions

Hi I have a Killer Sudoku from Puzzler #181 that the solver can't crack.

I'm not sure if it is because the strategy required hasn't been programmed or whether the puzzle is flawed.

If you are interested, is there a way I can send it to you ?

Many thanks

Pete

Thank you so much for all the work you have done and are doing in providing an excellent and probably the best resource there is for people interested in puzzles. Since the web site has been recovered I have not been able to get the Sudoku Solver -Solution Count button to work. It returns a SudokuWiki.org/404 on the address line and an "Article Not Found" as a result. It was working well for me before the crash. I am using Windows 10 and tried getting it to work with IE, Fire Fox and Chrome to no avail. Thanks again, Rich

So sorry about the vicious hack. I'm saddened that our world has people so evil as to destroy Andrew's site that has given pleasure to so many people the world over. When I was working I used to purchase monthly puzzle packs both as a way to support the site, and give me diversions on long flights. I especially enjoy the symmetrical patterns of the daily puzzles. I'm going back to purchasing monthly puzzle packs as a way to support the site financially.

Why the daily jigsaw does not display on the web page?
I have enabled Javascript.

Welcome back. You were very much missed.

Has the definition of 'midnight' changed as a result of the hack/restore? Not complaining at all, just asking.

I made a small donation...hopefully it helps a little with the recent hack. Hope it gets sorted out!

Well, seems there's a strategy that's not known by your solver. Cracking the cryptic found it. I call it odd/even. it's very usable by humans, and not any sort of bifurcation.

Divide the puzzle into odd/even columns (or rows).

In the odd columns (or rows) there must be a total of 20 evens, minus any that are already placed (4 per column).

now for each row, count the number of known evens. subtract that number from four. color that many squares that are on an odd columns. doesn't matter which ones.

now count the number of colored squares on the odd rows. if this is the same as the maximum left to place on those columns, then we can make some deductions.

Specifically if any row has all of it's cells in the odd columns marked as potential evens at this point, then you can eliminate odds from those squares. This is because placing an odd on one of them would mean there aren't enough spaces left to put all the evens.

On the rows you couldn't eliminate the odds from the odd columns, you can then eliminate the evens from the even columns on those rows, since all the evens MUST be in the odd columns. uncolor the odd cells, and color the empty even cells a different color.

This can be done with row and column swapped. Since there are less even numbers than odd, this technique usually works better with evens in the odd rows, or evens in the odd columns. smaller number, greater area.

Usually, this will get you nothing. But if you notice very few evens in the odd rows, or very few evens in the odd columns, this can give a useful result.

numbers 1 to 9 on the right side of sudoku?