The New Sudoku Players' Forum

[luismoreno]

-281-----
5-7--96--
9--7--4--
7---2--4-
6-1---2-5
-4--1---7
--4--7--6
---2-67-4
------92-


it has more than 1 solution if you solve it can you post 1 or 2 because I'm stuck on it

Can anyone delete this post

[sweetbix]

Code: Select all

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

Check that you entered the puzzle correctly. It has more than one solution.

[sweetbix]

luismoreno, you have asked for help to solve the puzzle even though it has more than one solution. Do you realise that you will get to a point beyond which logic cannot take you and then you will have to guess?

Up until the point of guessing, this puzzle can be solved by singles alone. Check this site for help with solving techniques Simple Sudoku. If you still want help then let us know how far you’ve got.

You may prefer to solve a puzzle which you can be sure has a unique answer. There are millions of them. You can download the Pappocom programme from this website, free trial for 28 Days. It will create unlimited valid puzzles for you.

[Crazy Girl]

luismoreno,
As the puzzle has more than one solution there is no way to solve it using LOGIC alone.

If you wish to solve the puzzle, you would have to guess which candidate is in a particular cell and see if you get a solution. This is called 'Trial and Error' and is not a technique used to solve sudoku's with only one solution.

but the best advice would be to find a new puzzle with one solution that you can solve with LOGIC.

The pappocom puzzle below is rated difficult, if you get stuck, post again and someone will give you a hint.

Code: Select all

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

[hisudoku]

but you have to check conflicts first. otherwise you have an empty answer.

[SHuisman]

There are actually 3 solutions, you can solve it by logic to this point:

Code: Select all

428|163|579
517|489|632
963|752|418
---+---+---
7..|628|341
681|374|295
342|915|867
---+---+---
2.4|8.7|156
1..|2.6|784
876|541|923

The remaining 7 cels can be 'solved' in 3 ways. If you want i can post them. But it think you know enough.

[ronk]

The remaining 7 cels can be 'solved' in 3 ways.

Which suggests the correct starting grid might have been ...

Code: Select all

 .28|1..|...
 5.7|..9|6..
 9..|7..|4..
 ---+---+---
 7..|.2.|.4.
 6.1|...|2.5
 .4.|.1.|..7
 ---+---+---
 ..4|..7|..6
 .9.|2.6|7.4
 ...|...|92.

... although that's not symmetrical.

[Ruud]

The remaining 7 cels can be 'solved' in 3 ways.

Which suggests the correct starting grid might have been ...

Code: Select all

 .28|1..|...
 5.7|..9|6..
 9..|7..|4..
 ---+---+---
 7..|.2.|.4.
 6.1|...|2.5
 .4.|.1.|..7
 ---+---+---
 ..4|..7|..6
 .9.|2.6|7.4
 ...|...|92.

... although that's not symmetrical.

This one is symmetrical:

Code: Select all

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

And it is very educational. It can be solved with singles and 1 finned x-wing.

So shall we start a 'make this sudoku unique and symmetrical' thread?

Ruud.

[ronk]

And it is very educational. It can be solved with singles and 1 finned x-wing.

All singles works pretty good too, and I don't think that's coincidence.

[edit: Oops, I didn't cut and paste your puzzle, but edited only the r8c3=9 into the starting grid ... and it solved with singles only. And I assume you meant sashimi x-wing.]

So shall we start a 'make this sudoku unique and symmetrical' thread?

Hmm! That could be fun.

[QBasicMac]

This one is symmetrical:

Nice work!

Mac

[QBasicMac]

I assume you (Ruud) meant sashimi x-wing.

Not familiar with sashimi x-wing.

Could you or someone point it out in detail? (Unless it is one of those techniques which assumes the puzzle has a unique solution, in which case I don't want to know.

Here is T&E which proves the puzzle has a unique solution.

r6c1=8 soon gets to here:

Code: Select all

+----------+-------------+-------------+
| 4  2   8 | 3    6  1   | 5   7    9  |
| 5  1   7 | 4    8  9   | 6   3    2  |
| 9  6   3 | 7    5  2   | 4   18   18 |
+----------+-------------+-------------+
| 7  9   5 | 6    2  3   | 18  4    18 |
| 6  3   1 | 8    7  4   | 2   9    5  |
| 8  4   2 | 9    1  5   | 3   6    7  |
+----------+-------------+-------------+
| 2  58  4 | {1}  9  7   | 18  158  6  |
| 1  58  9 | 2    3  6   | 7   58   4  |
| 3  7   6 | 5    4  {8} | 9   2    18 |
+----------+-------------+-------------+


Column 9 is clearly impossible.

Thus r6c1=3 which leads to unique solution.

Mac

[re'born]

Mac,

Basic techniques will get you to

Code: Select all

 *--------------------------------------------------*
 | 4    2    8    | 13   6    13   | 5    7    9    |
 | 5    1    7    | 4    8    9    | 6    3    2    |
 | 9    6    3    | 7    5    2    | 4    18   18   |
 |----------------+----------------+----------------|
 | 7    9    5    | 6    2    38   | 138  4    138- |
 | 6    38   1    | 38   7    4    | 2    9    5    |
 | 38*  4    2    | 9    1    5    | 38#   6   7*   |
 |----------------+----------------+----------------|
 | 2    358  4    | 18   9    7    | 138  158  6    |
 | 18   58   9    | 2    3    6    | 7    158  4    |
 | 138* 7    6    | 5    4    18   | 9    2    138* |
 *--------------------------------------------------*


In a perfect world, we would have a 3 in r69c19, thus forming an x-wing and allowing us to remove the 3 from r4c9. However, the 3 is missing from r6c9 and is replaced by a 3 in r6c7. It turns out that because r6c7 is a buddy of r4c9, that this is a not a problem and the same elimination can be made. r6c7 is called the fin (of the finned x-wing) and since the cell at r6c9 does not have a 3, this is even called a sashimi x-wing. For more details, see the link to finned fish in the advanced solving section sticky.

[QBasicMac]

It turns out that because r6c7 is a buddy of r4c9, that this is a not a problem and the same elimination can be made

Hey, thanks! Will add that pattern to my mental toolbox.

I have used the pure X-Wing so much that I have come to believe in the eliminations it identifies. In the beginning, I only used that pattern as a tool to identify a good place to do coloring.

I will probably do the same with the finned tool until I have used it 5 or 10 times, namely use it to find
r6c1=3 --> r9c1<>3 --> r9c9=3 --> r4c9<>3
r6c1<>3 --> r6c7=3 --> r4c9<>3

Thanks again,

Mac

[ravel]

You can also use the 2 strong links of the sashimi x-wing to eliminate 3 both in r4c9 and r7c7.

[ronk]

In the good ole days we would call the 'sashimi x-wing' a turbot fish. I sorta miss those days.