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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Tue Feb 03, 2009 5:39 pm Post subject: Set NNP_2 Puzzle 5 -- Advanced |
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| Code: | +-----------------------+
| 5 . . | 9 . . | . 6 4 |
| . . . | . . . | . 3 . |
| . . . | 5 . . | 9 . . |
|-------+-------+-------|
| 8 . 9 | 4 . . | 1 2 . |
| . . . | . . . | 8 5 7 |
| . . . | . . 2 | . . . |
|-------+-------+-------|
| . . 7 | 6 5 . | . 9 . |
| 9 6 . | 2 3 . | 7 . . |
| 1 . . | . 9 . | . . 3 |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Wed Feb 04, 2009 3:49 am Post subject: |
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| Code: | .------------------.------------------.------------------.
| 5 17 38 | 9 18 37 | 2 6 4 |
| 2467 9 26 | 18 24 67 | 5 3 18 |
| 246 124 38 | 5 24 36 | 9 7 18 |
:------------------+------------------+------------------:
| 8 3 9 | 4 7 5 | 1 2 6 |
| 246 24 126 | 3 16 9 | 8 5 7 |
| 67 57 156 | 18 168 2 | 3 4 9 |
:------------------+------------------+------------------:
| 3 8 7 | 6 5 1 | 4 9 2 |
| 9 6 4 | 2 3 8 | 7 1 5 |
| 1 25 25 | 7 9 4 | 6 8 3 |
'------------------'------------------'------------------' |
UR {2,4} in r23c15 says that the 6 can be removed from r5c1 because in order to avoid the deadly pattern, both the 2 and the 4 must exist in r5c1.
with that 6 gone, the resulting UR {2,4} in r35c12 makes a strong inference with the 1 in r3c2 and the 6 in r3c1, then forms this chain
UR24[(1)r3c2 = (6)r3c1] - (6=7)r6c1 - (7)r6c2 = (7)r1c2; r1c2 <> 1
and solves it. |
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Steve R
Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England
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| Posted: Wed Feb 04, 2009 12:17 pm Post subject: |
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In Norm’s grid an alternative route is to eliminate 7 from r2c1 using the W-wing with pincers (67) in r2c6 and r6c1. They are linked by the conjugates with respect to 6 in the third row.
If you prefer to assume the puzzle has a unique solution note where the completed cells contain 2 and 4:
| Code: | .------------------.--------------------.------------------.
| 5 17 38 | 9 18 37 | *2 6 *4 |
| 2467 9 26 | 18 24 67 | 5 3 18 |
| 246 124 38 | 5 24 36 | 9 7 18 |
:------------------+--------------------+------------------:
| 8 3 9 | *4 7 5 | 1 *2 6 |
| 246 24 126 | 3 16 9 | 8 5 7 |
| 67 57 156 | 18 168 *2 | 3 *4 9 |
:------------------+--------------------+------------------:
| 3 8 7 | 6 5 1 | *4 9 *2 |
| 9 6 *4 | *2 3 8 | 7 1 5 |
| 1 25 25 | 7 9 *4 | 6 8 3 |
'------------------'--------------------'------------------' |
The reverse BUG means that r9c3 cannot contain 2, again solving the puzzle in one step.
Steve |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Wed Feb 04, 2009 3:15 pm Post subject: |
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My solution was definitely more routine.
The UR <24> in r23c15 noted be Norm has a strong link on <4> in row <2> to delete <2> from r3c1.
That opens a xy-wing <246> with pivot <26> in r2c3 and then,
a xyz-wing <267> with pivot in r2c1 deletes <6> in r3c1 and completes the puzzle.
Both the observation by Norm regarding the UR <24> and the reverse BUG condition noted by Steve were very enlightening. Such views suggest still more techniques to solve a puzzle. My new buzz phrase is "look globally" 
Ted |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Wed Feb 04, 2009 6:15 pm Post subject: |
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| Quote: | In Norm’s grid an alternative route is to eliminate 7 from r2c1 using the W-wing with pincers (67) in r2c6 and r6c1. They are linked by the conjugates with respect to 6 in the third row.
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and to compliment the w-wing, there is a m-wing on {6,7}
which eliminates the 6 in r3c1
via cells, r6c1, r2c1, r2c6 and r3c6. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Mon Feb 09, 2009 1:40 am Post subject: |
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| I used the Hidden UR on 24, which exposed the XY-Wing on 264 and an M-Wing on 67 finished it. |
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