The New Sudoku Players' Forum

[tarek]

Do you have another example like this? I will find the time to complete it fully on paper, if I am able

This is another one, I can't post anymore of these (I need them for the book )

Code: Select all

 . . . | 3 . . | 8 . . 
 . . . | . 4 6 | . . . 
 . 1 . | 2 . . | . . 9 
-------+-------+------
 . 8 1 | . . . | . 7 . 
 . 9 . | . . . | 2 1 . 
 . . . | . . 2 | 6 . 3 
-------+-------+------
 8 . . | . . 4 | 1 2 . 
 . . 2 | 7 5 . | 3 . . 
 . . 7 | . . 1 | . 5 . 

Enjoy

Tarek

[CathyW]

Easier than your first one Tarek!

[tarek]

Easier than your first one Tarek!

You are right, This one has only triples & a swordfish and the usual doubles & xy wing, the other one had more of everything & a quad......

I think for you Cathy, these do not provide much of a challenge..... I will post something hopefully soon tailored for you.

Tarek

[CathyW]

Interesting! I didn't use a swordfish but did use simple colouring on 8s to make an elimination.

Thanks for your kind offer!

[Pat]

Hi Pat
Here are some samples from the book
(the book is divided in nine levels, with level 9 the hardest)---

many thanks, Carcul!!
i had hoped for just one sample or maybe two, to help me map Sheldon's ratings to the familiar ratings of the Pappocom puzzles — now with 5 examples, i find that Sheldon has Hard puzzles starting at the earliest levels (1,3) — and Very Hard puzzles at the highest levels (7–9) — which confirms your suggestion that he does not exceed the difficulty of the Pappocom puzzles.

thanks again!
~ Pat

[Heuresement]

To Tarek: Thanks you Tarek for stretching my abilities further

This second one was again a challenge for me to do on paper, but after persevering, I completed it by using a pencil to mark candidates. Once I had done all the obvious cells, I found two triples on row 3, and then a swordfish of 9s, which appeared to open it up. However, after filling in quite a few more cells, I came to another halt, and could not see any further openings. There were no more x-wings or swordfish that I could see, so resorted to looking for xy wings. However, at the same time, I noticed a short forcing chain that opened it up and finally completed it.
Unfortunately, I have now exceeded my allotted time for doing sudoku puzzles today, and really the rest of the week too. Oh well!

Thank you again

[tsheldon]

Dear all, especially Carcul and 9x9,

I've only just found this discussion thread of my book, Sudoku Genius - so I felt I'd better reply. A mixed reception it seems - I really feel like I've entered the lion's den of sudoku solvers here, I've never known such voracious appetites for difficulty.

When I was writing the book and compiling the puzzles, I had to make a decision where to place them in terms of difficulty to satisfy sudoku addicts without intimidating aspiring improvers. I also had to decide whether to include every technique or not. For brevity, I eventually decided to omit ones such as swordfish, uniqueness etc in the intro; and accordingly, they're not required to solve the puzzles. Of course, they might well be useful in solving the puzzles, and even make them easier. I realise solvers will use all the tools at their disposal, but thought it only fair that the book was a complete kit - ie that all the puzzles should be solvable by the techniques listed.

I was afraid of two things - people saying they were too easy, and people saying they were too hard. I didn't imagine I would get both complaints in equal measure, so I hope this means they are pitched about right... As for the puzzle I have deemed the hardest, I found that (during testing) this was the one that had the most people the most stuck for the most time. Perhaps, Carcul, you are just too skilful and have outgrown the mainstream of sudoku into a level of ability that would floor most of us!

I hope others are enjoying the book, and I welcome all comments at sudokugenius@hotmail.com.

Best wishes
Tom Sheldon

[Pat]

When I was compiling the puzzles,
I had to make a decision where to place them in terms of difficulty.

I decided to omit swordfish, uniqueness etc.

I was afraid of two things - people saying they were too easy, and people saying they were too hard.
I didn't imagine I would get both complaints, so I hope this means they are pitched about right.

Perhaps, Carcul, you are just too skilful
and have outgrown the mainstream of sudoku into a level of ability that would floor most of us!

hey, tsheldon, nobody said the puzzles were too tough!

whereas the description (at Amazon) states:

144 of the hardest puzzles in the world
ending with a final puzzle that only the most hardened Sudokuist will crack

indeed Carcul is too skilful

but you'd have had less complaints if you'd just stated at the outset
that your puzzles match the Hard and Very Hard puzzles of Pappocom.
(which means that they are indeed pitched about right for me.)

~ Pat

[lunababy_moonchild]

Hello Tom and welcome to the Sudoku Players' Forums.

I thought that it was mighty brave of you to post, and am delighted to hear what you have to say.

I haven't tried your book so can't comment on that but thanks for paying us a visit and I hope you stick around to enjoy the discussions

but you'd have had less complaints if you'd just stated at the outset
that your puzzles match the Hard and Very Hard puzzles of Pappocom.

Pat, it is my personal opinion that it is not necessary to rate puzzles according to Pappocom ratings (that said, I have dubbed a few into the program to see what it said) and - again my opinion - I think that finding out different ratings for different puzzles is as much fun as finding decent puzzles to solve. Simply because I have found that puzzles set by different people solve differently and as such the rating is arbitrary. Ratings are such a difficult thing to get right anyway.

Speaking of setting puzzles, Tom are the ones in your book hand-crafted or computer generated?

Luna

[Pat]

it is my opinion that it is not necessary to rate puzzles according to Pappocom ratings (that said, I have dubbed a few into the program to see what it said) and — again my opinion — I think that finding out different ratings for different puzzles is as much fun as finding decent puzzles to solve. Simply because I have found that puzzles set by different people solve differently and as such the rating is arbitrary. Ratings are such a difficult thing to get right anyway.

i had read Carcul's complaint that the puzzles were too easy; but i was concerned that Carcul is just such an expert solver that the puzzles might be too tough for me — as the book-description (at Amazon) promised "144 of the hardest puzzles in the world" — and they would be too tough for me if they needed anything beyond X-wing — so i loaded those samples into the Pappocom software merely to find out if they'd be accepted — and they were, none even called "Unfair" — which the author/publisher could've told us in advance — and then Carcul would've had no cause to complain.

yes, rating the puzzles is pretty tough — but how do we find decent puzzles to solve without some system of rating them?

Sheldon's puzzles happen to be Just Right — for me at my present level.

·:·:· Pat

[lunababy_moonchild]

yes, rating the puzzles is pretty tough — but how do we find decent puzzles to solve without some system of rating them?

Sheldon's puzzles happen to be Just Right — for me at my present level.

·:·:· Pat

Indeed, one of the (in my view, happy) challenges that we face. This is why I personally want to know who it is that is setting the puzzles and whether or not they are computer generated (and if the book doesn't say so, I don't buy it). I know that I can trust Pappocom - and yes, I've dubbed a few puzzles into the software myself - and I know that I can trust Nikoli. I have bought a book by Pete Sinden (this was an accident, since I had actually set out to buy a book by Peter Sterling, after reading on the Daily Mail website about how he sets the puzzles for the Daily Mail and how he had improved his puzzle setting from the early days) and was pleasantly surprised by it - these were some of the puzzles I dubbed into Pappocom's software!

I still look at the books that are available and if they state the puzzle setter and method of setting and have some kind of introduction about what the author thinks makes a good sudoku, and it rings true with what has been stated here, then I have a fair idea that it is a reputable book.

At this stage it's still trial and error but if the book is brave enough to state who sets the puzzles and how they are set then they have given at least some thought to the process and not just churned out 1,000 puzzles or so to generate income because Sudoku is popular just now.

I think that Tom Sheldon's book has an introduction and some hints and tips on how to solve - I didn't read it that closely though - which implies that he put some thought into his book. There is also a website listed, if I recall correctly.

Yes, it is difficult to know who's puzzles are reputable and/or hard enough. Seems to me it's a matter of looking at what's available and making your choice. Or posting to this website and asking if anybody's heard of it (Peter Greene anybody?).

Luna

[emerson]

this book only confirms that hard puzzles cannot be found in published books.
Regarding the last and (theoretically) toughest puzzle of this book, it's one of the most simple that I have solved.

Carcul, you are an expert solver - what you consider a simple puzzle may not be so simple to me!

perhaps someone would post just one sample puzzle from this book?

~ Pat

I will give you a more fair review. This book has the most consistently challenging puzzles of any I've seen published.

I will add that I am not the typical solver. I am part of the group that likes to solve using no mark ups, no coloring, no note taking of any kind. Everything must be done in your head. I do this because I play chess and blackjack, where note taking during games is not permitted and taking of notes at sudoku would not exercise my brain in the way that I want... which is to solve problems using both logic and memory. I believe that unless you are a very advanced solver who uses lots of note taking solving techniques that you will like this book a great deal. I also believe that those who are at only about the 20 percentile of the group using the advanced techniques will find a challenge in this book.

[emerson]

it is my opinion that it is not necessary to rate puzzles according to Pappocom ratings (that said, I have dubbed a few into the program to see what it said) and � again my opinion � I think that finding out different ratings for different puzzles is as much fun as finding decent puzzles to solve. Simply because I have found that puzzles set by different people solve differently and as such the rating is arbitrary. Ratings are such a difficult thing to get right anyway.

i had read Carcul's complaint that the puzzles were too easy; but i was concerned that Carcul is just such an expert solver that the puzzles might be too tough for me � as the book-description (at Amazon) promised "144 of the hardest puzzles in the world" � and they would be too tough for me if they needed anything beyond X-wing � so i loaded those samples into the Pappocom software merely to find out if they'd be accepted � and they were, none even called "Unfair" � which the author/publisher could've told us in advance � and then Carcul would've had no cause to complain.

yes, rating the puzzles is pretty tough � but how do we find decent puzzles to solve without some system of rating them?

Sheldon's puzzles happen to be Just Right � for me at my present level.

�:�:� Pat

I agree with your comments. But I will add that I don't think there is a variation in difficulty between the various sections of this book. The difficulty level will depend entirely on the order in which you employ various solving techniques. I don't use any specific order (other than looking for gimmies at the start). Sometimes a puzzle that took a while to solve would have seemed very simple if I had employed a different technique at the start... which I might have in another puzzle.

[Luke]

I will give you a more fair review. This book has the most consistently challenging puzzles of any I've seen published.

The level nine ("hardest") puzzle in the book was posted earlier in this thread, so anyone can have a go at it. It solves with nothing more than a couple hidden triples. By today's standards these puzzles simply don't have any teeth.