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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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 Posted: Wed Dec 08, 2010 2:07 am Post subject: Nataraj, November 4 Advanced |
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| 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 |
+-------+-------+-------+
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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: 3854
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| Posted: Wed Dec 08, 2010 4:51 am Post subject: |
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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
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| Posted: Wed Dec 08, 2010 4:58 am Post subject: |
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| 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: 3854
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| Posted: Wed Dec 08, 2010 5:15 am Post subject: |
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| 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
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| Posted: Wed Dec 08, 2010 9:02 am Post subject: |
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As alluded to there are a bunch of solutions to this one - especially with DPs. A common factor seems to be (3 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: 3854
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| Posted: Wed Dec 08, 2010 9:38 am Post subject: |
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| 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 |
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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
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| Posted: Wed Dec 08, 2010 2:31 pm Post subject: |
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| Danny, thanks - you have point out m-rings to me before! I keep forgetting about them. |
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