The New Sudoku Players' Forum

[The Druid]

I have noticed that, in all the (Times, and Times Book) Su Doku puzzles I have done, there is always at least ONE of each numeral shown on the grid (before I start filling it in, that is).

So there is always at least one #1, one #2, one #3, one #4, one #5, one #6, one #7, one #8 and one #9 displayed, before I pick up my pencil.

I'm interested ... are there any Su Doku puzzles which do NOT show at least one of each numeral printed on the grid?

It seems to me that it should be possible to complete a Su Doku puzzle correctly with one numeral missing completely from the initial grid, but possibly not with more than one numeral missing completely... though this is "gut feeling" on my part rather than anything else.

[Animator]

There are...

Let me see if I can find some in my Sudoku Archive :)

[Animator]

No idea where this came from: (could be the Times or the program)

8 * * | * * 5 | 7 3 4
* * * | 8 * * | * * 2
4 6 * | 2 * * | * 1 *
-----------------------
* 5 3 | * * 1 | * * 7
* * * | * * * | * * *
2 * * | 7 * * | 4 5 *
-----------------------
* 4 * | * * 3 | * 2 8
1 * * | * * 4 | * * *
3 2 7 | 6 * * | * * 5

Another one: the 10th puzzle of the library 'Time Trial 1': ( http://forum.enjoysudoku.com/viewtopic.php?t=57 )

A 'Very hard' one:

1 * * | * * 4 | * * *
8 5 * | * * 1 | * * 3
* 4 * | * 9 * | * * *
-----------------------
* * 2 | * * 3 | * 8 *
* * 8 | * * * | 1 * *
* 1 * | 4 * * | 6 * *
-----------------------
* * * | * 5 * | * 6 *
3 * * | 9 * * | * 5 8
* * * | 6 * * | * * 2

The Times (I guess): 23 March

3 * * | 9 * * | 5 * *
* * 9 | * * * | * 3 7
* * * | * 7 * | * * 2
---------------------
* * * | 4 * * | * 6 *
5 * 7 | * * * | 3 * 1
* 9 * | * * 3 | * * *
---------------------
9 * * | * 1 * | * * *
6 5 * | * * * | 4 * *
* * 1 | * * 9 | * * 5

[The Druid]

Excellent - thank you.

I shall now go offline and do those three!

[Animator]

Only three? I posted four of them... one was a link though :)

[The Druid]

Unfortunately, the link requires me to download a library book - and the library book will only operate with the Su Doku program. The Su Doku program will not run on my (relatively modern, fairly-high-spec) 'puter, no matter what I do, so there does not seem much point in downloading the library book.

But many thanks for the other three... they kept me happily amused for a little while!

[Animator]

It's just an XML file... you can download it and open it in notepad (or wordpad or word or...) ...

but to safe you the troule:

Puzzle 10: Medium:

3 6 * | * 2 * | * 8 9
* * * | 3 6 1 | * * *
* * * | * * * | * * *
---------------------
8 * 3 | * * * | 6 * 2
4 * * | 6 * 3 | * * 7
6 * 7 | * * * | 1 * 8
---------------------
* * * | * * * | * * *
* * * | 4 1 8 | * * *
9 7 * | * 3 * | * 1 4

[The Druid]

Thank you, Animator - it's appreciated!

[Pat]

indeed it is from The Times ( March 23, 2005 ) No 99 RATING: DIFFICULT

- Pat

The Times (I guess): 23 March

Code: Select all

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


[Pat]

and here's another one - this has 17 clues

for the source, please see gfroyle ( 2005.Jul.11 )

- Pat

Code: Select all

 5 . 2  . . .  4 . .
 8 . .  7 1 .  . . 3
 . . .  . . .  . . .

 . . .  . . 4  6 . .
 . 7 .  2 . .  . . .
 . 1 .  . . .  . . .

 6 . .  . . 2  . . .
 . . .  . 3 .  . 1 .
 4 . .  . . .  . . .


[The Druid]

Thanks for supplying that additional 17-number puzzle, Pat.

I found it rather strange and disorientating to look at, as it wasn't symmetrical - I don't think I have done a Su Doku without a pattern before, and I kept wondering whether there were some numerals missing or misplaced!

However, it was very simple and straightforward to do ... until near the end.

That's when I realised that there seemed to be more than one solution to placing the last few digits.

Can someone please confirm that there is more than one solution to this puzzle?

Many thanks

The Druid

[PaulIQ164]

The puzzle only has one solution. I'd check you sopied it right before you started solving, otherwise post where you got stuck.

[The Druid]

The puzzle only has one solution. I'd check you sopied it right before you started solving, otherwise post where you got stuck.

Thanks, Paul. But I didn't get stuck at all... I took one way out but believe that there is at least one alternative route. I'll check the alternative(s).

Are you another member of Mensa?

The Druid

[Karyobin]

Doubt it, he thinks 'sopied' is a word today. What with 'poopsed' the other day he'll have the basics of a new language by Christmas.

In response to your original post, I would personally think it impossible to have a sudoku with a unique solution wherein the original clues leave out two or more numbers. That would surely lead to two or more solutions wouldn't it?

[PaulIQ164]

I took the proper MENSA IQ test, but I was determined too smart to spend forty quid a year to join.

Obviously is a grid has two numbers missing from the clues, there'll always be at least two solutions. If it's the 1s and 2s missing for example, once you've found one solution, you can swap the 1s and 2s and you'll definitely have another solution. I seem to remember some discussion a while ago as to whether these count as truly 'different' solutions, as the choosing of which digit to put in which place is essentially arbitraty. As to whether you can get a puzzle with two numbers not present in the clues, but with only one possibility for which 9 of the 18 cells one of the numbers goes in, I think that's unresolved, but I'd imagine it to be true.

Sorry that that didn't make much sense, but it's rather hard to explain.