The New Sudoku Players' Forum

[EHoward]

Another tough one (I think)...I got to this point, and then stuck. Sudoku Helper site stated the next solution step was some generalized chain, and it was too convoluted for me to actually follow it....so....I was wondering if there were some of the easier ways to get to the next step (e.g. locked and unlocked cells and blocks, open/hidden pairs/triples/quads, xy-wing).
I'm willing to learn some new techniques, as long as they are not toooo way out there....(I think I understand some of the x-cycle stuff, but haven't found an opportunity in my puzzle to use it...?)

Thanks in advance to anyone who can help with next steps...

EHoward

Code: Select all

+----------------------+----------------------+----------------------+
| 267    8      1      | 457    257    2567   | 37     9      347    |
| 2679   479    26     | 347    237    267    | 5      8      1      |
| 3      47     5      | 9      1      8      | 267    24     2467   |
+----------------------+----------------------+----------------------+
| 28     35     23     | 3578   6      4      | 9      1      2378   |
| 4      1      9      | 378    2378   27     | 23678  5      23678  |
| 268    356    7      | 1      9      25     | 238    234    2348   |
+----------------------+----------------------+----------------------+
| 79     79     8      | 2      4      3      | 1      6      5      |
| 5      36      4     | 678    78     1      | 238    23     9      |
| 1      2      36     | 568    58     9      | 4      7      38     |
+----------------------+----------------------+----------------------+


[ChrisT]

My solver tells me that it is an invalid puzzle - there are multiple solutions. Where did you get it from? Have you missed off a clue by mistake?

Chris

[tarek]

My solver tells me that it is an invalid puzzle - there are multiple solutions. Where did you get it from? Have you missed off a clue by mistake?

Hi EHoward & ChrisT,

I also had several solutions (6 to be exact)

[EHoward]

It is from Rofact International Inc. in a magazine called SUDOKU purchased from a magazine store. It's not one of the more well known publications.

Not sure if it helps or means anything, but it does have a solution in the magazine, but if there are truly multiple solutions, then it's not worth all the time I put into it I guess....grr...

Next time I'll put the original puzzle into Sudoku Helper to see if it 'works' before I start on the actual puzzle.

Original puzzle:

-81 --- -9-
--- --- 5-1
--- -64 9--
41- --- -5-
--7 19- ---
--- 2-3 --5
5-4 --- ---
-2- --- 47-[/code]

[udosuk]

Dear EHoward,

Firstly, the "original puzzle" you posted is missing an entire row. It's probably the 3rd row, and if according to your version, the puzzle is probably:

Code: Select all

. 8 1 . . . . 9 .
. . . . . . 5 . 1
3 . . 9 . 8 . . .
. . . . 6 4 9 . .
4 1 . . . . . 5 .
. . 7 1 9 . . . .
. . . 2 . 3 . . 5
5 . 4 . . . . . .
. 2 . . . . 4 7 .

Yielding 6 solutions.

However, guessing from the symmetry, you probably missed one clue at R5C9, which should be 7 to give a puzzle in normal difficulty (see note). So the original puzzle is probably:

Code: Select all

. 8 1 . . . . 9 .
. . . . . . 5 . 1
3 . . 9 . 8 . . .
. . . . 6 4 9 . .
4 1 . . . . . 5 7
. . 7 1 9 . . . .
. . . 2 . 3 . . 5
5 . 4 . . . . . .
. 2 . . . . 4 7 .

And this is a perfectly valid sudoku puzzle giving 1 unique solution.

If the source magazine is as prestigious as you described, than this is probably what they published and you might have mistakenly omitted that clue when you transcribe it... However everything is just my speculation so pardon me if I'm wrong and it's truly the magazine that's at fault...

Note:
If R5C9=3, the resulting puzzle has 4 solutions and is not valid.
If R5C9=6, we still get a valid puzzle but it requires very advanced techniques (e.g. bifurication chains) or T&E to solve. Interested readers could try it themselves.

Code: Select all

. 8 1 . . . . 9 .
. . . . . . 5 . 1
3 . . 9 . 8 . . .
. . . . 6 4 9 . .
4 1 . . . . . 5 6
. . 7 1 9 . . . .
. . . 2 . 3 . . 5
5 . 4 . . . . . .
. 2 . . . . 4 7 .

All other values give puzzles with no solution.