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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Thu Apr 08, 2010 5:40 pm Post subject: Puzzle 10/04/08 (B) |
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| Code: | +-----------------------+
| 1 . . | . . . | . . . |
| . 6 . | . . . | . 2 . |
| . . 2 | . 6 . | . . 3 |
|-------+-------+-------|
| . . . | . 7 . | 3 8 . |
| . . 3 | 8 . 6 | . 5 . |
| . . . | . 1 3 | . 6 7 |
|-------+-------+-------|
| . . . | 5 . . | 7 . 4 |
| . 7 . | 6 4 9 | . 3 2 |
| . . 4 | . . 7 | 6 9 8 |
+-----------------------+
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Thu Apr 08, 2010 8:34 pm Post subject: |
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Two steps.
| Quote: | To prevent the UR18 in r23c67, r2c6 =4 or r2c7=9: UR18[(4)r2c6 = (9)r2c7]r23c67 - (9=8)r1c7 - (8=7)r1c3 - (7=4)r1c8; r1c6<>4
AIC found by extending the vertex of a potential xy-wing:
(4=3)r1c2 - (3=9)r2c1 - r6c1 = r6c4 - (9=7)r3c4 - (7=4)r3c8; r1c8<>4
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Ted |
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Thu Apr 08, 2010 8:45 pm Post subject: |
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W-wing didn't help but a little xy-chain made it two steps...
| Quote: | xy-chain (8=9)r2c5-(9=7)r3c4-(7=4)r3c8-(4=7)r1c8-(7=8)r1c3; r1c6<>8, r2c3<>8
Type 1 UR (18) r23c67; r2c6=4 |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Thu Apr 08, 2010 9:59 pm Post subject: |
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| Hint wrote: | Two VH steps should do it.
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Thu Apr 08, 2010 10:20 pm Post subject: |
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| daj95376 wrote: | | Hint wrote: | Two VH steps should do it.
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Danny, how about a | Quote: | xy-wing -789 with vertex in r2c5, and a
Type 1 UR18.
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But why use a short simple set of steps when big steps are available?
Ted |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Apr 09, 2010 12:42 am Post subject: |
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| After basics, this puzzle looked pregnant with UR and DP possibilities. But first I used an XY-Wing (897) which exposed a puzzle-ending Type 2 UR (18-4), although Ted had it as a Type 1. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Fri Apr 09, 2010 2:08 am Post subject: |
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| Marty R. wrote: | | After basics, this puzzle looked pregnant with UR and DP possibilities. But first I used an XY-Wing (897) which exposed a puzzle-ending Type 2 UR (18-4), although Ted had it as a Type 1. |
Marty, here is my code after basics:
| Code: | *-----------------------------------------------------------*
| 1 349 78 | 2379 5 248 | 89 47 6 |
| 349 6 78 | 379 89 148 | 189 2 5 |
| 459 459 2 | 79 6 18 | 18 47 3 |
|-------------------+-------------------+-------------------|
| 2469 1249 69 | 249 7 5 | 3 8 19 |
| 7 1249 3 | 8 29 6 | 24 5 19 |
| 249 8 5 | 249 1 3 | 24 6 7 |
|-------------------+-------------------+-------------------|
| 2369 239 69 | 5 238 28 | 7 1 4 |
| 8 7 1 | 6 4 9 | 5 3 2 |
| 235 235 4 | 1 23 7 | 6 9 8 |
*-----------------------------------------------------------* |
As you can see, it cannot be a Type 2 UR. Cleanup after the xy-wing removes the 9 in r2c7 making the Type 1 condition.
We must have had different code after basics.
Ted |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Apr 09, 2010 3:53 am Post subject: |
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| Quote: | | We must have had different code after basics. |
I don't have any intermediate grids but clearly I had a 4 in r3c6 for reasons unknown. I also seem to recall that I had a bivalue in r1c6. Who knows? |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Apr 09, 2010 4:41 am Post subject: |
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Ted, I wasn't planning on doing this again. However, I just did the Diabolical from Sunday and it went in 15 minutes, so with the extra time I did this again. Here I am after basics. I don't see how the 4 in r3c6 was disposed of. 
| Code: |
+---------------+--------------+-----------+
| 1 349 78 | 2379 5 248 | 89 47 6 |
| 349 6 78 | 379 89 148 | 189 2 5 |
| 459 459 2 | 79 6 148 | 189 47 3 |
+---------------+--------------+-----------+
| 2469 1249 69 | 249 7 5 | 3 8 19 |
| 7 1249 3 | 8 29 6 | 24 5 19 |
| 2459 24589 58 | 249 1 3 | 24 6 7 |
+---------------+--------------+-----------+
| 2369 239 69 | 5 238 28 | 7 1 4 |
| 8 7 1 | 6 4 9 | 5 3 2 |
| 235 235 4 | 1 23 7 | 6 9 8 |
+---------------+--------------+-----------+
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Play this puzzle online at the Daily Sudoku site |
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