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Nataraj, November 4 Advanced

 
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Wed Dec 08, 2010 2:07 am    Post subject: Nataraj, November 4 Advanced Reply with quote

Code:

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

Play this puzzle online at the Daily Sudoku site

XY-Loop starting in r3c4 and ending in r3c6. Except it's probably not an XY-Loop because not all cells involved were bivalue. So what should it be called?

At any rate, based on assigned and deleted number, r7c5<>7.
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Wed Dec 08, 2010 4:51 am    Post subject: Reply with quote

Hmmm! Besides everything else, there's a <157> DP in r367c56.

Code:
 after basics
 +--------------------------------------------------------------+
 |  1     8     3     |  5     4     2     |  9     6     7     |
 |  5     4     7     |  6     3     9     |  8     1     2     |
 |  2     6     9     |  78   *17+8 *17    |  5     4     3     |
 |--------------------+--------------------+--------------------|
 |  7     9     58    |  2     5-8   6     |  4     3     1     |
 |  38    13    6     |  48    9     14    |  2     7     5     |
 |  4     15    2     |  3    *157  *157   |  6     9     8     |
 |--------------------+--------------------+--------------------|
 |  6     2     1     |  47   *57   *57+34 |  37    8     9     |
 |  38    357   58    |  9     6     37    |  1     2     4     |
 |  9     37    4     |  1     2     8     |  37    5     6     |
 +--------------------------------------------------------------+
 # 28 eliminations remain

(8)r3c5                                             - (8)r4c5

(3-4)r7c6 = (4)r7c4 - (4=8)r5c4                     - (8)r4c5

(4-3)r7c6 = (3)r8c6 - (3=8)r8c1 - (8)r8c3 = (8)r4c3 - (8)r4c5
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Wed Dec 08, 2010 4:58 am    Post subject: Reply with quote

I looked at that DP and don't know why I didn't carry it further.
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Wed Dec 08, 2010 5:15 am    Post subject: Reply with quote

Marty R. wrote:
I looked at that DP and don't know why I didn't carry it further.

If you knew of all the convolutions I went through to get it to work, you'd be glad that you skipped it!!!
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Wed Dec 08, 2010 9:02 am    Post subject: Reply with quote

As alluded to there are a bunch of solutions to this one - especially with DPs. A common factor seems to be (3Cool strong links in column 1?

Here's one just using the (17)UR and what Ted called external SIS (I think!)...
Code:
(17)URr36c56 external SIS
{r3} (7)r3c3 ; r7c4<>7
{b5} (1)r5c6 - (1=3)r5c2 - (3)r5c1=r8c1 - (3=7)r8c6 ; r7c4<>7

It is also interesting that overlaid on top of the (17)UR is an m-wing...
Code:
m-wing(17) ; (7=1)r3c6 - r3c5=(1-7)r6c5=r6c6 ; r78c6<>7
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Wed Dec 08, 2010 9:38 am    Post subject: Reply with quote

peterj wrote:
It is also interesting that overlaid on top of the (17)UR is an m-wing...
Code:
m-wing(17) ; (7=1)r3c6 - r3c5=(1-7)r6c5=r6c6 ; r78c6<>7

Nice find Peter! Call it an M-Ring and you can add r6c5<>5.
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Wed Dec 08, 2010 2:31 pm    Post subject: Reply with quote

Danny, thanks - you have point out m-rings to me before! I keep forgetting about them.
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