The New Sudoku Players' Forum

[ghfick]

I must pass along a concern about a recently published book of puzzles. The book is called 'Sudoku Extreme Volume 1' by AD Ardson. I tried the very first puzzle in this book and I did not get very far. While labeled 'extreme', I became suspicious and so checked the solution count using Andrew Stuart's solver site. The puzzle does not have a unique solution. I have now checked the next 5 puzzles and all fail to have a unique solution. Ardson has published many books of puzzles but this is the first one to receive my attention. I have left a message of concern on his website and his email but so far I have not received a response. Clearly, the 'solutions' in the back of this book offer just one of the many possible 'solutions'. Here are the first 6:

.4.2..3...93......2..1...45.....56.2..28.14..8.56.....62...3..4......27...1..2.3.
....7.8.69..5..4....7....35...43...262.....491...92...37....6....6..9..32.5.4....
....362..6.8..4..9..9....4.5..78....1.4...7.3....41..8.4....8..8..4..1.7..219....
..2..3.7...5.6..2.1...27..8..7..56...6.....9..4.6..5..7..35...6.5..1.2...3.4..7..
.8......61..64.5...57..3....7..9..68...8.4...81..5..9....9..62...9.32..12......5.
.46....9.5...6........846.562.....5...46721...7.....641.572........1...2.3....51.

Best
Gordon

[dobrichev]

Hi ghfick,

I am confirming that the puzzles you posted if follow the traditional rules have multiple solutions.

Code: Select all

.4.2..3...93......2..1...45.....56.2..28.14..8.56.....62...3..4......27...1..2.3.   28   18
....7.8.69..5..4....7....35...43...262.....491...92...37....6....6..9..32.5.4....   28   47
....362..6.8..4..9..9....4.5..78....1.4...7.3....41..8.4....8..8..4..1.7..219....   28   43
..2..3.7...5.6..2.1...27..8..7..56...6.....9..4.6..5..7..35...6.5..1.2...3.4..7..   28   21
.8......61..64.5...57..3....7..9..68...8.4...81..5..9....9..62...9.32..12......5.   28   9
.46....9.5...6........846.562.....5...46721...7.....641.572........1...2.3....51.   29   427


I don't know what 'Sudoku Extreme Volume 1' is.
Seems that either the author goofed, or there are additional constraints for these puzzles which you neglected.

If you are sure there are no additional rules and it is entirely authors goof, you may copy these along with a link to the publication in the dedicated thread http://forum.enjoysudoku.com/sudokus-of-shame-t3071.html.

[Botchee]

Unique solutions were why I took down tophatpuzzle.com, but since have learned how to do my own programming, to create a sliding puzzle with its unique shape. I've finally escaped my code cave, but the world has gone whacky with this Covid-19 thing!

<-- dude's running a fever <--

[m_b_metcalf]

I took another look at these puzzles. The first 5 of the 6 'solve' with a simple backdoor. Maybe the sixth can be 'solved' by a less simple backdoor.

Could it be that the puzzles were generated using a backdoor technique, among others, something that should not be done?

Mike

[International_DBA]

This is an interesting post, at least for me.
The Amazon preview of this book only shows four puzzles.
I have checked the first one and according to Andrew Stuart it has multiple solutions, as you have already suggested.

You say you have checked more than four of these puzzles and they all have multiple solutions.
I assume from this that you have paid real money to buy this book.
Am I correct?

I recently published my own book of 400 tough sudokus (all with a Hodoku grade between Hard(1000) and Hard(1999)).
All the puzzles are minimal and all have exactly one solution.
Sales have so far been disappointing, to say the least.
In fact I have only sold four copies.

There has been so little interest in the book that a recent attempt to give away a copy via a free to enter competition has so far produced zero entries.
You will find it in the Books section of this forum.

With a little effort I imagine that I could amend my puzzle creation software to produce a book of 400 extreme puzzles.
They would all have a Hodoku grade greater than Extreme (5000).
Would there be a market for a book like this?
It would retail on Amazon for $6.99 unless their prices increase in the meantime.

I would need around 100 confirmed pre orders before starting on such an exercise.
My 400 tough puzzles required around 12 hours of computing time to create as I had to reject almost 8000 puzzles because they had the wrong grade.
Creating 400 extreme puzzles would probably require several days of computing time as only around 1% of the puzzles I create come out as extreme.

[m_b_metcalf]

With a little effort I imagine that I could amend my puzzle creation software to produce a book of 400 extreme puzzles.
They would all have a Hodoku grade greater than Extreme (5000).
Would there be a market for a book like this?
It would retail on Amazon for $6.99 unless their prices increase in the meantime.

If one goes to the books section of amazon.co.uk and searches for 'sudoku', 75 pages of books are displayed, at 16 per page. Looks as though there's lots of competition! My impression is that the top-selling books (based on them having a large number of reviews) are those published by newspapers, trade publishers and games magazines. They all have their own publicity and distribution channels. Probably the only way to be a top-selling author is to pitch a book to the professional publishers. As it's so easy to generate puzzles*, there's obviously a lot of competition from would-be authors. On this forum, we're certainly not short of puzzles to solve, so that's why there is zero interest here.

HTH

Mike

* Folks here have access to many generators. I used one to generate 400 mid-range minimal puzzles. That took 5 minutes, with a further 4 minutes to rate them with SukakuExplainer. The number of clues was bewteen 21 and 27. A sample of them is hidden below.

Hidden Text: Show

Code: Select all

...3..8.4..8...7....5.4.....14.....6.7.....42...57......162.........8..363...9..1   ED=4.4/1.2/1.2   
........4...69..21..9..2.5...2.....3..6.8.....4.2.9...2...4.5..6....8...8.431..6.   ED=4.5/1.2/1.2   
.8...14.......672..2........9...8.....7..4.3.6..9...4....8..2....2.6.8...4..3..5.   ED=4.6/1.5/1.5   
8.......3.5......4...7.85...............863..4.65..7.2..9.4...1.32..5.....1..7...   ED=5.6/1.2/1.2   
.58.....9......36.......8.2.7..4...3..3.9..2.6...72.....29...57.3.......48..27...   ED=5.9/1.2/1.2     
.8..4...7....13.5.4.....21...23....98...9.3.......2.......57.9..2...47....79...8.   ED=6.6/1.5/1.5   
..41.....2...6.3....9....2.5...3...8.6..9714........6.7........9.8..37.....4...9.   ED=6.7/1.2/1.2   
63..28..9..1.9..8..........9..2..6.8.2.536.4...........4...72....5.4.7...6...1...   ED=6.8/1.2/1.2   
....9...63.1...4......25..1..7..86.9...2..8.....9472...9.6.....8.5.....2..4......   ED=6.9/1.5/1.5   
3.9......2...1.36.4.6.2...7....78......9....8......9.19874....5...........47.1.2.   ED=7.0/1.2/1.2   
.4...1.....35.....9.....16..347..9..7..68..23...........6...21..5...27....84.....   ED=7.1/2.3/2.3   
.....2.6....9.......5.3.2.81....89..5.2.....7..61..5..697.4...38..2.6............   ED=7.2/1.2/1.2   
.....9..3.712..6..........4..53..7...478.....69...72.....1.8..5......4...82.4....   ED=7.3/1.5/1.5   
..4..8.6.72...3.4.6..2........9..37.......4.13....2..9.5.....8..86..7.....36..1..   ED=7.5/1.2/1.2   
...653....3.7.92...........8.......6..1...7.......2.3.29...53.7.7..6...1..3...6..   ED=7.6/1.2/1.2   
.....5...8..17......5..93...69.....1.8.6.7.5.5.2......4...2..8....3.12.....4....7   ED=7.7/1.2/1.2   
.5.34....926......4......97....3.......7...5654.1...2.6.......5.79....3.....8..61   ED=7.8/1.2/1.2   
.4.9.....8....2.9.9...1..6...9...6....57.4..1..83....4.2....5.......12.7..3....4.   ED=8.2/1.2/1.2   
.7...5..2...69.7...923...5.......3...5.7...2..618.......74..5..3......1.6...3.8.7   ED=8.3/1.2/1.2   
...5.14.......2.1...6.8..9..1....7.6..48.......9....3..9.....7....675..85..4.....   ED=8.4/1.2/1.2   
5....719........7...8.6.4...7.4.9.2...9.8...31........34.29..........3.....85...7   ED=8.5/1.2/1.2   
6.....5...371........4....1...64...5.6.3.5.14........64.8..39..2...7.......2....3   ED=8.9/1.2/1.2