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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Mon Nov 02, 2009 10:55 pm Post subject: Set XY_03 Puzzle 050 |
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Several choices.
| Code: | XY puzzles can be solved using these techniques:
Basics: Naked/Hidden Single, Naked Pair/Triple, Locked Candidates 1/2
Basics+: Naked Quad, Hidden Pair/Triple/Quad
VH: BUG+1, UR Type 1, X-Wing, XY-Wing
VH+: 2-String Kite, Empty Rectangle, Remote Pair, Skyscraper,
XYZ-Wing, finned X-Wing, UR Type 2/4
XY: gM-Wing, W-Wing, XY-Chain, BUG+2, BUG+3, other URs
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| Code: | +-----------------------+
| . 2 . | 9 7 . | 3 . 4 |
| 6 . . | . . 3 | . 2 . |
| . . . | 6 . 4 | . . . |
|-------+-------+-------|
| 3 . 2 | 1 . . | . . . |
| 5 . . | . . . | . 4 . |
| . 1 9 | . . 6 | . . 3 |
|-------+-------+-------|
| 1 . . | . . . | 4 . . |
| . 6 . | . 9 . | . 1 2 |
| 2 . . | . . 1 | . 5 6 |
+-----------------------+
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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: Mon Nov 02, 2009 11:35 pm Post subject: |
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| Code: | .---------------.---------------.---------------.
| 8 2 1 | 9 7 5 | 3 6 4 |
| 6 7 4 | 8 1 3 | 59 2 *59 |
| 9 35 35 | 6 2 4 | 18 7 18 |
:---------------+---------------+---------------:
| 3 4 2 | 1 58 *78 | 6 9 *57 |
| 5 8 6 | 27 3 9 | 127 4 17 |
| 7 1 9 | 24 45 6 | 25 8 3 |
:---------------+---------------+---------------:
| 1 *-59 78 |*57 6 2 | 4 3 *789 |
| 4 6 35 | 35 9 *78 | 78 1 2 |
| 2 39 78 | 347 48 1 | 789 5 6 |
'---------------'---------------'---------------' |
(5=7)r7c4 - (7=8)r8c6 - (8=7)r4c6 - (7=5)r4c9 - (5=9)r2c9 - (9)r7c9 = (9)r7c2; r7c2 <> 5 |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Wed Nov 04, 2009 5:38 am Post subject: |
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| W-Wing on 78 takes out the 7 from r9c7, exposing a puzzle-ending Kite on 7. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Thu Nov 05, 2009 2:58 pm Post subject: |
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A one stepper using an ALS, marked *.
| Code: |
*--------------------------------------------------*
| 8 2 1 | 9 7 5 | 3 6 4 |
| 6 7 4 | 8 1 3 | 59 2 59 |
| 9 35 35 | 6 2 4 | 18 7 18 |
|----------------+----------------+----------------|
| 3 4 2 | 1 58 78 | 6 9 57 |
| 5 8 6 | 27 3 9 | 127 4 17 |
| 7 1 9 | 24 45 6 | 25 8 3 |
|----------------+----------------+----------------|
| 1 59 78* | 57 6 2 | 4 3 789* |
| 4 6 35 | 35 9 78 | 78 1 2 |
| 2 39 78 | 347 48 1 | 789 5 6 |
*--------------------------------------------------* |
ALS[(7)r7c39 = (9)r7c9]r7c39 - (9=5)r2c9 - (5=7)r4c9 - (7)r5c79 = (7)r5c4; r7c4<>7
Ted  |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Thu Nov 05, 2009 6:59 pm Post subject: |
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[Edit: Just me rambling. Decided it was a distraction.]
Last edited by daj95376 on Fri Nov 06, 2009 12:02 am; edited 1 time in total |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Thu Nov 05, 2009 8:03 pm Post subject: |
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Danny,
I understand your presentation of the chain, but I view it more like using the "hidden pair" approach frequently posted by Norm rather than viewing it as a ALS. This ALS is so simple that it could be viewed in both ways. I am attempting to learn how to use ALS and therefore that is how I presented this chain when I found it; it is my first such successful (?) ALS.
As for notation, I tried to use the Eureka notation suggested by Asellus in his recent post in
Eureka Notation Question in the "Solving Techniques forum.
Ted |
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oaxen
Joined: 10 Jul 2006
Posts: 96
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| Posted: Fri Nov 06, 2009 10:19 am Post subject: |
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| The one stepper starts with "9" in r7c2. The other "9" in r7c9 shows after a few moves to be impossible. |
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wapati
Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.
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| Posted: Fri Nov 06, 2009 11:12 pm Post subject: |
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| oaxen wrote: | | The one stepper starts with "9" in r7c2. The other "9" in r7c9 shows after a few moves to be impossible. |
Why did you pick that cell and that value? |
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oaxen
Joined: 10 Jul 2006
Posts: 96
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| Posted: Sat Nov 07, 2009 9:37 am Post subject: |
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"wapati"
Why did you pick that cell and that value?
My answer
I always try to find a place to start a chain. For that I need two same numbers in a row or a column. Normally then I have many possibilities. It is rather easy to see what will happen if I follow the pairs. Most of them gives nothing, but some will give me a long chain. If the first choice is incorrect the other must be true. With one eliminated almost ever it is a "one stepper". |
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