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Strategies for Popular Number Puzzles
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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...
Sunday 16-Nov-2025
... by: Kate, Manchester, UK
However, I am struggling to get it to solve puzzle no 157 from dailysudoku.com
https://www.dailykillersudoku.com/search?n=157
Their solution has 2 & 8 in H1 & J1 but Killer Sudoku Solver deduces that it should be 3 & 7 - and then it comes up with an error in G6 as it wants to put a 3 in this cell (when it should be a 2)
Load Puzzle
Keep up the good work
I’ve been struggling find a bug that is giving false positives on innies/outies giving a bad path down the line as you have discovered. It only seems to happen after the solver service has been running a few days, very odd. Anyway as of the update tonight you should be fine. I’ve put the link above if you need to load it again. Use “Email this board” to send me puzzles, especially if the muck up like that, very valuable report
Sunday 16-Nov-2025
... by: Henon, Austria
When you got a set of numbers highlighted and edit numbers it may happen that some cells get updated but the highlighting is not recalculated for those cells. That may result in overlooking numbers and making mistakes. As it is now, after making edits you have to un-highlight the numbers and highlight them again. All you need to do is remember the set of highlighted numbers and recalculate the highlighting for all cells. Thanks!
Saturday 15-Nov-2025
... by: Anonymous, USA
Load Sudoku: CLICK TO LOADhttps://www.sudokuwiki.org/Tridagons
In the Tridagon strategy, the solver is missing some eliminations in the "More than one Guardian" scenario.
One of the examples from Phil's folly (linked from the page):
........1.....2.3...4.15.......346...47..8.1.6.31.78...78...1.63...8..744.67.138.
After applying basic strategies, there is a tridagon pattern on candidates 259 in boxes 4679, with 2 guardians digits: 1 in r4c3 and 1 in r8c3. Since the guardians are all the same digit, and since the candidate 1 in r2c3 sees all of the guardians, it should be eliminated.
Friday 7-Nov-2025
... by: Philip, United Kingdom
Friday 7-Nov-2025
... by: TenPeter, USA
Tuesday 28-Oct-2025
... by: Susan, United States
Monday 27-Oct-2025
... by: Hawkeye, US
Sunday 26-Oct-2025
... by: Sid, France
Working on the nice example of XY-Chain appearing in the Daily Sudoku of 10/22, I noticed that while symbol 2 is actually highlighted in green or red at the chain ends, in the solved grid, the solution is symbol 2 at both ends.
I can assume that this is possible because of the weak links, but I still can't figure out exactly why ? Is there some more to say to explain this ? For example, does the length of the chain have something to do with this ? Are there examples of chains having same ends and different lengths ?
Many thanks and the best.
Sid
Saturday 25-Oct-2025
... by: Doll Hellmut, Germany
Friday 24-Oct-2025
... by: Karwan N, Sweden
I want to suggest that the highlighting function of the solver primarily uses high-contrast colors (red & green for instance) no matter which number is highlighted. For instance, 6:s & 7:s are very hard to spot against the white background and the 2:s and 4:s are the easiest.