I'm stuck, what do I do next?

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I'm stuck, what do I do next?

Postby Burner172 » Fri Jun 09, 2006 4:07 am

Hello,

I'm stuck with this puzzle....I don't see a pattern that I could use to elminate other numbers....I've looked for two's and three's ......

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

If you could just give me a hint or two as to which patterns I should use to elminiate other numbers, I'd appreciate that. thanks!
Burner172
 
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Postby tarek » Fri Jun 09, 2006 6:01 am

Hi there,

!st of all u need to post at this level the pencil marks of your progree to know for sure your progress

Im posting the next possible steps & highlighting the cells & you need to figure out the pattern & elimination(s)
Code: Select all
*--------------------------------------------------------*
| 9     12    127  | 178   4     5    | 3     6     78   |
| 6     3     17   | 9    %78    2    | 4    %18    5    |
| 8     5     4    | 17    3     6    | 2     19    79   |
|------------------+------------------+------------------|
| 5     128   129  | 6     189   3    | 7     4     89   |
| 4     18    19   | 2     1789  78   | 5     3     6    |
| 7     6     3    | 5    %89    4    | 1    %89    2    |
|------------------+------------------+------------------|
| 1     4     5    | 78    6     78   | 9     2     3    |
| 3     7     6    | 4     2     9    | 8     5     1    |
| 2     9     8    | 3     5     1    | 6     7     4    |
*--------------------------------------------------------*

*-----------------------------------------------*
| 9    12   127 | 178  4    5   | 3    6    78  |
| 6    3    17  | 9   %78   2   | 4   %18   5   |
| 8    5    4   |%17   3    6   | 2    19   79  |
|---------------+---------------+---------------|
| 5    128  129 | 6    19   3   | 7    4    89  |
| 4    18   19  | 2    179  78  | 5    3    6   |
| 7    6    3   | 5    89   4   | 1    89   2   |
|---------------+---------------+---------------|
| 1    4    5   | 78   6    78  | 9    2    3   |
| 3    7    6   | 4    2    9   | 8    5    1   |
| 2    9    8   | 3    5    1   | 6    7    4   |
*-----------------------------------------------*
tarek
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Postby emm » Fri Jun 09, 2006 6:12 am

Hi there too

The solver lists these techniques for solving the puzzle

1. locked candidates – the 1s in the centre box
2. X wing – the 8s in row 2 and 6
3. XYwing - which Tarek has highlighted

Click on Simple Sudoku for enlightenment. The XY wing is covered in this forum thread.
emm
 
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Postby Burner172 » Fri Jun 09, 2006 11:21 am

Hi,

Thanks so much for your help! Yeah I did catch the locked pattern for 1's in centre box.

I don't understand how you used X wing pattern to remove the 8's in 5th/6th row (5th column)?

What did you look at that helped you removed those 8's? You said row 2 and 6.... I see possible candidates as being 78, 18, 89, 89 in "x pattern" what does that mean? how does that "tells me" that other 8's in the column would be impossible?

Again, thanks
Burner172
 
Posts: 3
Joined: 08 June 2006

Another Solution

Postby Carcul » Fri Jun 09, 2006 11:35 am

Code: Select all
 *-----------------------------------------------------------*
 | 9     12    127   | 178   4     5     | 3     6     78    |
 | 6     3     17    | 9     178   2     | 4     18    5     |
 | 8     5     4     | 17    3     6     | 2     19    79    |
 |-------------------+-------------------+-------------------|
 | 5     128   129   | 6     189   3     | 7     4     89    |
 | 4     18    19    | 2     1789  78    | 5     3     6     |
 | 7     6     3     | 5     89    4     | 1     89    2     |
 |-------------------+-------------------+-------------------|
 | 1     4     5     | 78    6     78    | 9     2     3     |
 | 3     7     6     | 4     2     9     | 8     5     1     |
 | 2     9     8     | 3     5     1     | 6     7     4     |
 *-----------------------------------------------------------*

[r2c3]=7=[r1c3]-7-[r1c9]-8-[r2c8]-1-[r2c3], => r2c3<>1 and the puzzle
is solved. Check here for the notation.

Carcul
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Postby Burner172 » Fri Jun 09, 2006 11:48 am

Hi

I mean I could understand how Xwing would help if all four boxes had same pair of candidates (in this case, 8 and 9) then I'd know that two of these boxes would have to be 8 and be on the opposite end of X)

But the pairs I have is 18, 78, 89, 89 so?

The XY pattern, you looked at r2c5, r3c4, and r2c8? ok I'll have to look at the XY pattern rule and see how it works
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Postby emm » Fri Jun 09, 2006 11:51 am

The Xwing works on a single candidate, not a pair.

The 8 must be at either of the two diagonal points of the X - either r2c5, r6c8 or r2c8, r6c5 - otherwise you would have two 8s in one column.

Try it out - either way there can be no 8 at r45c5.
emm
 
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Joined: 02 July 2005

I'm stuck, what do I do next?

Postby Cec » Fri Jun 09, 2006 1:23 pm

Burner172 wrote:"..The XY pattern, you looked at r2c5, r3c4, and r2c8? ok I'll have to look at the XY pattern rule and see how it works"

Hi also Burner172,

The following link explains the XY-wing pattern:
http://forum.enjoysudoku.com/viewtopic.php?p=17589&sid=73be1e77936ebee5f10ef87aceb046c3#17589

In your puzzle, after the 1 is excluded from r2c5, the top three rows look like this where the three cells marked with an asterisk form the XY-pattern:
Code: Select all
 *-----------------------------------------------------------*
 | 9     12    127   | 178   4     5     | 3     6     78    |
 | 6     3     17    | 9     78*   2     | 4     18*    5    |
 | 8     5     4     | 17*   3     6     | 2    X19    79    |
 |-------------------+-------------------+-------------------|

Candidates [78] in r2c5 form the "stem" cell with candidates [17] and [18] being the "branch" cells. Provided you understand the explanation of the XY-pattern in the above link then as candidate 1 in cell r3c8 can "see" both the 1's in cells r2c8 and r3c4 ("see" implies sharing the same two groups) then candidate 1(designated X) can be excluded from cell r3c8 which then solves the puzzle with only singles remaining.

Cec
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