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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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 Posted: Wed Mar 26, 2008 8:37 pm Post subject: From a thread in another forum, years ago ... |
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Enjoy!
| Code: | Puzzle #1
+-------+-------+-------+
| . . . | . . 6 | 8 . 5 |
| . . . | . . 1 | . 6 7 |
| . . 4 | . 5 . | . . . |
+-------+-------+-------+
| . . . | . . 7 | . . 3 |
| . 6 . | . 1 . | . 4 . |
| 5 . . | 2 . . | . . . |
+-------+-------+-------+
| . . . | . 9 . | 2 . . |
| 9 1 . | 5 . . | . . . |
| 8 . 7 | 3 . . | . . . |
+-------+-------+-------+ |
Keith |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Thu Mar 27, 2008 12:22 am Post subject: |
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| It was a very cluttered grid at the start, but an XY-Wing and UR finished it off. |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Thu Mar 27, 2008 3:57 pm Post subject: |
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Only experts here ? Marty's UR is not an ordinary one:
| Code: | *-------------------------------------------------------*
| 1237 379 1239 | 4 23 6 | 8 39 5 |
| 23 359 2359 | 89 238 1 | 4 6 7 |
| 6 8 4 | 7 5 39 | 139 1239 129 |
|------------------+---------------+--------------------|
| 124 249 1289 | 6 48 7 | 159 12589 3 |
| 237 6 2389 | 89 1 5 | 79 4 289 |
| 5 479 189 | 2 348 39 | 1679 189 1689 |
|------------------+---------------+--------------------|
| 34 345 356 | 1 9 #48 | 2 7 #468 |
| 9 1 26 | 5 7 #248 | 36 38 #468 |
| 8 24 7 | 3 6 24 | 159 159 19 |
*-------------------------------------------------------* |
Strong links for 4 in r8 and c9 and for 8 in r7 and c6 eliminate 8 in r78c9 and r8c6 and 4 in r7c6.
Alternative: r78c9=6 => r8c7=3 and r8c6=2 => r8c3=6 => r8c7=3. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Thu Mar 27, 2008 5:07 pm Post subject: |
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| Quote: | | Marty's UR is not an ordinary one: |
You give me too much credit. I have no idea of how to replicate my solution from your grid, but my notes indicate an XY-Wing 28-12-18 and a Type 1 UR on 23 in boxes 12. Being a paper-and-pencil guy, I have no intermediate grids. |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Thu Mar 27, 2008 6:17 pm Post subject: |
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Cant reconstruct your solution path.
Anyway, there can be made eliminations with the UR 23 in the grid above either (r12c15):
The 2 in r1c1 can be eliminated directly due to the strong link for 2 in c5.
A bit more:
Either r2c5=8 or we have a type 1 UR, which eliminates 23 in r1c1.
r2c5=8 => r2c4=9 => r2c123=235 => r1c2<>23
So in both cases 23 cannot be in r1c1.
But its not a big help.
Another "useless" elimination i found was with the 39-pairs. The grouped strong links both for 3 an 9 in row 3 between column 4 and box 3 make the 39's in r1c8 and r6c6 a remote naked pair - one must be 3, one 9.
So 9 cannot be in r6c8. |
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Victor
Joined: 29 Sep 2005
Posts: 207
Location: NI
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| Posted: Thu Mar 27, 2008 11:12 pm Post subject: |
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| The UR in 48s isn't 'standard' but it's not particularly difficult to see either. (Sorry, guess that sounds snooty, but compared to many exciting things explained in this forum by Ravel and many others, this ain't a very big deal.) |
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