Wednesday, April 3, 2013

Grille de la semaine #25 [League of Extraordinary Ladies and Gentlemen #12]

La création d'une grille ne se déroule pas toujours comme prévu. Il m'a été demandé la semaine dernière de préparer un Sudoku Extra Regions, une variante des plus communes mais que je n'ai que peu travaillée en tant d'auteur. Ayant rapidement eu quelques idées, j'ai décidé de tenter l'aventure et me suis lancé dans la fabrication d'une telle grille ; malheureusement il est impossible de tout maîtriser, et je n'ai jamais pu concrétiser exactement ce que j'avais en tête. J'ai donc légèrement dévié de ma voie et, tout en conservant la base de la grille que j'avais échoué à faire naître (motif des régions et premières déductions), l'ai revisitée en y adjoignant une règle supplémentaire me permettant d'inclure des éléments logiques intéressants. Le résultat est une grille qui, sans atteindre la difficulté des n°22 ou 24, demeure d'un bon niveau si l'on fait l'effort de s'abstenir d'employer des hypothèses.
Pour rappel, les grilles de la League sont désormais jouables en ligne à l'adresse avec un délai de 24h.

You can't always get what you want. Last week I was asked to make an Extra Regions Sudoku; a common variant but with which I am not that much experienced as an author. Since I quickly got a few ideas, I decided to give it a try and started working on a puzzle. Unfortunately one cannot control everything and I could never get exactly what I had in mind. So I somewhat strayed from my path and, while keeping the base of the grid I could not bring to life (pattern of extra regions and early deductions), reshaped it by adding an extra rule which would allow me to include some other interesting logical steps. The result is a puzzle which, without attaining the difficulty of n°22 or 24, is still quite challenging if you play it fair and refrain yourself from guessing.
Remember that you can now solve the puzzles from the League online on with a 24h delay.

Règles :
Chaque ligne, colonne et région, ainsi que chacune des régions grisées, doivent contenir les chiffres de 1 à 9.
Si et seulement si deux cases symétriques l'une de l'autre par rapport au centre de la grille contiennent le même chiffre ou si leur somme est égale à 10, elles sont marquées de deux traits diagonaux.
Each row, column and region, as well as each of the shaded areas, must contain the digits from 1 to 9.
If and only if two cells that are symmetric to each other regarding the center of the grid either contain the same digit or have their sum equal to 10, they are marked with two short diagonal lines.

#27 Extra Regions Sudoku With Mirrored Cells



  1. Hi Bastien.First and foremost thnks for creating an Extra - regions which i asked for last week.It must have been a bit difficult for you as you have stated that you have never created Extra - regions before.
    But now i feel that i should not have asked you for this Extra-regions :)
    I tried solving this sudoku yesterday on sudoku cup.Within 15 mins i got stuck.I utilised Buddy cells very early and filled up the middle box very quickly .It was very nice!!!Nice construction.
    But my experience from the 15th minute to the 50th minute was to say the least horrible :( . Even with intense focus i could not proceed beyond the point in which i got stuck.I tried all known tricks
    looking for singles,doubles,Buddy cells and still could not proceed beyond that.
    I am sorry to say this but i strongly disagree with you when you state this sudoku does not attain the difficulty of week 22,24 (Figures, Irregular)
    This sudoku is much,much,much more difficult than those 2 especially irregular is nothing compared to this sudoku.
    I am very disappointed that i m not able to find the right logical continuation.I know i can complete with bifurcation but i dont wnt to do that way.Somehow you create those sudokus where the gap between a certain point and then finding the next point is too huge.Not that i am complaining but certainly this is not the right mix of difficulty that you ought to impose on sudokus.These sudokus are of a very high difficulty that only say a doctor sudoku or a Tiit Vunk will solve easily.But from an average solver's point of view this is not one that can be completed(through logic alone) which defeats the purpose of creating sudokus that are meant to be solved only through logic.
    To conclude ,pl.create sudokus that are solvable from an average sudoku solver's point of view as the frustration that comes up when not being able to complete after spending 50 mins on a single sudoku is too huge to cope up.I would request you to alternate the difficulty levels.One week can be medium ,one week can be easy and the next week hard(but certainly not as hard as this one).But the last few weeks greater than killer ,figures and this one now...Difficulty is too skewed .You are not providing easier sudokus :(
    And one more improvement that i would love to see is in case if you are bent on creating only sudokus of these beastly kind as the above pl. provide the spoilers also at specific points which you think would be difficult to proceed beyond.
    I hope you take my suggestions in the right sense and dont feel otherwise..........

  2. Hi,
    Actually I was referring to puzzles #22 and 24 (not weeks), hence Greater Than Killer and Figures, on which even the best solvers had lots of trouble. The Irregular was definitely easier than this one indeed, but looking at the timings of most players, the majority of them would certainly agree with me when I say that the Greater Than Killer was tougher. Anyway - I agree (and said) that this is a hard puzzle; but I feel like you are being a bit unfair when you say that I don't publish easier sudokus. Just look at the last three weeks: you have got an easy Thermo Sudoku, then a medium Irregular and now this hard Extra Regions. I think this fits quite well with what you are asking for. If I follow this pattern, I should post an easy puzzle next week, so just be patient for a few more days. ;-)
    As an author, estimating the difficulty of a puzzle is something that is really hard to do, in particular when the solving path is quite narrow, as is the case here. Looking at the replay of Hideaki Jo on, I could see that he solved the puzzle pretty much the way I expected him to, just he took "lots of time" to see things that seemed obvious to me (like the central region), but the problem is that everything is obvious when you know where and what to search. So, excepted in a few cases, I cannot really say before I publish a puzzle "this is a hard but doable one" or "this one is so tough nobody will find the path". I can only label such puzzles as hard and see what happens - and warn players that my hard puzzles usually deserve their title. Maybe it could be of some help to include a "notation system" like the one Fred Stalder put on his blog? I would be interested by your opinion here.

    About your last suggestion: actually, such a thing has been in my mind for some time and I am planning to publish hints on how to solve some of my puzzles. I think this can be a pretty good deal since I don't want to stop publishing hard sudokus, for several reasons (they are the most interesting to make; also, a large part of my audience is made of top solvers who need some challenge; and there is more).
    So, in short:
    - there will still be tough sudokus on this blog; be cautious when you see one.
    - I will try to alternate levels of difficulty on a a/b or a/b/c base (easy/hard or easy/medium/hard).
    - a few days after I publish a hard puzzle I will give a few spoilers - or even describe the full solving path, but if so I may restrain to only some of them since it will take more time to do. No final decision yet, I may as well do both depending on the puzzle.

    Finally, thanks for the comment. I insist that I always welcome constructive and polite feedback. I hope I answered your concerns and that my desire of publishing more hard puzzles will not make you flee away; I definitely care a lot about non-pro players, I just don't want to oppose both approaches. My wish will always be to provide fun to all ranges of solvers.