The first successful Sudoku Challenge respondent

Sun August 23 2020 10:09amSudoku

A few days ago, an astute visitor***** to the CyberJerry Sudoku page successfully responded to the Sudoku Challenge, the first CyberJerry visitor to do so. He found the Sudoku grid pictured which the Analyzer couldn't solve, and told me (in Spanish) how to solve it:

este sudoku lo saque de la pagina https://www.sudoku-online.org de categoria sudoku extremo #717, y su analizar dice que no tiene una solución, sin embargo por metodo analitico encuentro que F6 = 4 debido al 4 de E3 y el 4 de G5, tambien encuentro que I9 = 5 debido al 5 de D8 y al 5 de H4, al colocar estos dos números, ahora si dice que tiene solución única lo anterior esta pasando por que su analizador no está realizando el método más sencillo que es de eliminación directa o único número de la caja, mira la celda I1 = 8 se obtiene por ese métodotranslated to English:

this sudoku is taken from webpage https://www.sudoku-online.org category extreme sudoku #717, and your analyzer says it has no solution, however by an analytic method I find that F6 = 4 due to the 4 in E3 and the 4 in G5, also I find that I9 = 5 due to the 5 in D8 and the 5 in H4, upon placing these two numbers, now it says that it has one unique solution the above is happening because your analyzer isn't executing the simplest method which is direct elimination or the cell's only number, see how cell I1 = 8 is obtained by this method

*****The Challenger is:

Manuel Navarro De La Hoz

birthplace: Galapa del departamento de Atlántico, país Colombia

his YouTube channel: Mr cocogames

I have reviewed the Sudoku in question and have confirmed that my Analyzer does indeed fail to solve it, and that Señor Navarro has described a correct method for solving it. As promised, I am hereby acknowledging the success and superior Sudoku skills of Sr Navarro, and am also working at correcting the problem in the Analyzer.

Congratulations and thanks to Sr Navarro!

2 comments | rev. Sat Aug 29 8:31am |

Now that it's more and more difficult to find Sudoku grids that the CyberJerry Sudoku Analyzer (the 'Analyzer') can't analyze step by step, the great Sudoku Challenge is also becoming more difficult. To help out a bit, below are four Sudoku grids that the Analyzer can't analyze step by step. You just have to figure out how to solve one of these analytically (no guesswork) to qualify as a successful Sudoku Challenger. Click on any of the grids to bring it up in the Analyzer. Both it and you should be able to solve several cells. But at some point, the Analyzer gets stuck and can't give a hint. Can your brain keep analyzing beyond that point, and solve the puzzle? If so, click on the corresponding 'Answer Challenge' link and tell me how you did it. As before, I promise to publish your success.

~~With my brain, I know how to analyze and solve one of the grids below; am not telling which one~~.^{(Note 1)} But programming the Analyzer to do it would be a bear, and am very unlikely to tackle that job in the near future. Even less likely for the other three, which my brain can't (yet) figure out. So you have lots of time to meet this challenge. Good luck!

**Note 1 (17 July 2020):** It was the third one that i could solve with my brain but thought too difficult to program the Analyzer to solve. Surprisingly, after correcting a minor bug, the Analyzer now solves it, in a way that my brain hadn't anticipated. Looks like my brainchild is smarter than my brain. So, anyway, the third one above is now a different Sudoku, one that, like the other three, neither my brain nor the Analyzer can analyze step-by-step.

0 comments | rev. Fri Jul 17 7:49pm |

When the Unique Rectangle technique is unavoidable

Fri June 19 2020 9:24pmSudoku

A recent round of minor enhancements and corrections has made the CyberJerry Sudoku Analyzer capable of analyzing increasingly tough Sudokus. Two results: the "New Puzzle" control now offers a "Genius" level, and the "Hint" feature may offer extremely complex hints, containing many interdependent sub-steps of a variety of advanced strategies. The added focus on complex Sudokus has had another unforeseen result: the possibility of encountering what I call the "**Unavoidable Avoidable Rectangle**". (Not being able to find any mention of the phenomenon in any other website, I claim the right to assign this name to it.) Let me explain: (read article)

0 comments | rev. Thu Jun 25 7:40pm |

This blog article serves as both another bug report and as a candidate for the Sudoku Challenge .

This time, the Sudoku Analyzer cannot solve the Sudoku step-by-step. It should be able to. This is a known bug, recently discovered by yours truly, and which yours truly is working on, and hope to have fixed soon.

In the meantime, if you think you can solve this Sudoku analytically (no guesswork), (read article)

1 comment | rev. Fri Jun 5 9:45pm |

This Sudoku puzzle has me scratching my head.

The Sudoku Analyzer solves it step by step, giving clues along the way. Which is to say, it is not one of those occasional Sudokus which can only be solved in trial-end-error guesswork manner. But at a couple points, the Sudoku Analyzer gives very complex hints where simple hints are possible. This is not according to design. Then, in at least one very complex hint, several secondary hint steps are omitted, without which the complex hint is incomplete.

What's especially baffling is that these (read article)

0 comments | rev. Fri May 22 7:59pm |

The Great CyberJerry Sudoku Challenge has been answered

Wed August 1 2018 8:10pmSudoku

7-plus months ago this blog unveiled the great CyberJerry Sudoku Challenge. (See Jerry's Blog article of Dec 14 2017 for details.) In brief, the challenge is to provide a step-by-step analytical solution to a Sudoku that has CyberJerry's Sudoku Analyzer stumped. To meet the Challenge, the Sudoku must qualify thus:

(read article)

- 1. The Sudoku has exactly one solution.
- 2. CyberJerry's 'Analyze' button reports that the Sudoku cannot be rated, and at some point the 'Hint' button fails to provide a Hint.
- 3. You can describe a step-by-step analytical way to solve the Sudoku. You need only do so at the point(s) where the Sudoku Analyzer fails to provide a Hint. Note

3 comments | rev. Dec 4 2018 12:34pm |

After several years of development, testing, debugging, and improving the strategies, I am ready to proclaim that my Sudoku Analyzer is the best on the web, that it can analyze and give a step-by-step solution to even the toughest Sudoku.

**Please note that this does NOT entail simply giving a solution, but in providing a step-by-step analytical method to solve.**And so today I am unveiling the great CyberJerry Sudoku Challenge.

To be sure, I am still discovering some rare Sudokus for which the CyberJerry Sudoku Analyzer cannot give step-by-step analytical hints. But for those Sudokus, neither can anyone else. Or so I claim. (read article)

0 comments | rev. Dec 4 2018 7:58pm |