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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Fri Dec 26, 2008 10:01 pm Post subject: Set H Puzzle 13 |
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| Code: | +-----------------------+
| . . 2 | . 4 . | . . 7 |
| . 8 . | . . . | 4 . . |
| 1 . 6 | 3 . . | 2 . . |
|-------+-------+-------|
| . . 8 | . . . | 9 4 . |
| 2 . . | . 9 . | . . 6 |
| . . . | . . 3 | . . . |
|-------+-------+-------|
| . 2 7 | 9 . . | 6 . 1 |
| . . . | 8 . . | . . . |
| 3 . . | . 2 . | 7 . 9 |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Sun Dec 28, 2008 12:35 am Post subject: |
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I used six steps to solve this puzzle but have no idea what was really required; three steps were URs with overlaying x-wings!
| Quote: | skyscraper <3>
ER <5>
UR <59> with x-wing <9>
UR <57> with x-wing <7>
UR <67> with x-wing <7>
xyz <156>
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Ted |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Fri Jan 02, 2009 8:30 am Post subject: |
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| Code: | .---------------------.---------------------.---------------------.
| 59 359 2 | 156 4 15689 | 1358 13569 7 |
| 7 8 *359 | 1256 156 12569 | 4 13569 *35 |
| 1 4 6 | 3 578 5789 | 2 59 58 |
:---------------------+---------------------+---------------------:
| 56 13567 8 | 12567 156 1256 | 9 4 *235 |
| 2 1357 *135 | 4 9 158 | 1358 1357 6 |
| 4 15679 159 | 12567 1568 3 | 158 157 258 |
:---------------------+---------------------+---------------------:
| 8 2 7 | 9 35 4 | 6 35 1 |
| 569 1569 159 | 8 13567 1567 | 35 2 4 |
| 3 156 4 | 156 2 156 | 7 8 9 |
'---------------------'---------------------'---------------------' |
the marked skyscraper on 3's goes a long way.
then I found this mixed w-wing extended blah blah blah chain....
| Code: | .------------------.------------------.------------------.
| 59 59 2 |*16 4 8 |*13 136 7 |
| 7 8 3 | 2 *16 9 | 4 16 5 |
| 1 4 6 | 3 *57 *57 | 2 9 8 |
:------------------+------------------+------------------:
| 56 1567 8 | 1567 -156 2 | 9 4 3 |
| 2 3 15 | 4 9 *15 | 8 7 6 |
| 4 67 9 | 67 8 3 | 15 15 2 |
:------------------+------------------+------------------:
| 8 2 7 | 9 *35 4 | 6 *35 1 |
| 569 1569 15 | 8 1357 1567 |*35 2 4 |
| 3 156 4 | 15 2 156 | 7 8 9 |
'------------------'------------------'------------------' |
basically the strong links on 5 in row 3 connect the {3,5} cell in r7c5 and the {1,5} cell in r5c6, which makes either the 1 or the 3 true. do a little extening from the 3 and get this chain to elimate the 1 in r4c5 to solve it.
(1=5)r5c6 - (5)r3c6 = (5)r3c5 - (5=3)r7c5 - (3)r7c8 = (3)r8c7 - (3=1)r1c7 - (1)r1c4 = (1)r2c5; r4c5 <> 1 |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Fri Jan 02, 2009 7:42 pm Post subject: |
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Or, that's a 9-cell XY-Chain.
Here's a shorter ALS Chain that does the trick:
(5)r4c4|(5)r89c6 - (5=1)r5c6 - ALS[(1)r4c5=(5)r4c15] - (5)r4c4=(5)r9c4 - (5)r4c4|(5)r89c6; r4c4|r89c6<>5
Descriptively, r5c6 is <5> or <1>. If <1>, the 56 naked pair in r4 means r4c4 is not <5> so r9c4 must be <5>. Thus, r5c6 and/or r9c4 must be <5>, eliminating <5> from r4c4 and r89c6. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Fri Jan 02, 2009 8:25 pm Post subject: |
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| 6 steps like Ted - but I started with an ER on <3> that went a long way. Then an x wing on 7; Type 4 URs on 57 and 59; an ER on 5 and the xyz wing <156>. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Mon Jan 05, 2009 2:15 am Post subject: |
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| Asellus wrote: | Or, that's a 9-cell XY-Chain.
Here's a shorter ALS Chain that does the trick:
(5)r4c4|(5)r89c6 - (5=1)r5c6 - ALS[(1)r4c5=(5)r4c15] - (5)r4c4=(5)r9c4 - (5)r4c4|(5)r89c6; r4c4|r89c6<>5
Descriptively, r5c6 is <5> or <1>. If <1>, the 56 naked pair in r4 means r4c4 is not <5> so r9c4 must be <5>. Thus, r5c6 and/or r9c4 must be <5>, eliminating <5> from r4c4 and r89c6. |
very nice !!  |
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