Numerals on Grid

Everything about Sudoku that doesn't fit in one of the other sections

Numerals on Grid

Postby The Druid » Mon May 23, 2005 5:33 pm

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.
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Postby Animator » Mon May 23, 2005 5:40 pm

There are...

Let me see if I can find some in my Sudoku Archive :)
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Postby Animator » Mon May 23, 2005 6:08 pm

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
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Postby The Druid » Mon May 23, 2005 8:37 pm

Excellent - thank you.

I shall now go offline and do those three!:D
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Postby Animator » Mon May 23, 2005 8:49 pm

Only three? I posted four of them... one was a link though :)
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Postby The Druid » Tue May 24, 2005 5:14 pm

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!:D
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Postby Animator » Tue May 24, 2005 5:27 pm

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
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Postby The Druid » Thu May 26, 2005 6:40 pm

Thank you, Animator - it's appreciated!
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Postby Pat » Thu Aug 04, 2005 12:36 pm


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

- Pat


Animator ( 2005.May.24 ) wrote:
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


Last edited by Pat on Sun Aug 07, 2005 10:19 am, edited 2 times in total.
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17-clue puzzle, clues contain only 8 of the symbols

Postby Pat » Thu Aug 04, 2005 12:43 pm



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 . .  . . .  . . .
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Postby The Druid » Tue Aug 09, 2005 2:29 pm

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
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Postby PaulIQ164 » Tue Aug 09, 2005 2:39 pm

The puzzle only has one solution. I'd check you sopied it right before you started solving, otherwise post where you got stuck.
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Postby The Druid » Tue Aug 09, 2005 2:49 pm

PaulIQ164 wrote: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?

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Postby Karyobin » Tue Aug 09, 2005 3:06 pm

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?
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Postby PaulIQ164 » Tue Aug 09, 2005 3:17 pm

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.
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