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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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 Posted: Sat Apr 19, 2008 11:04 am Post subject: LA Times / Freep 18 April, 2008 |
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Not yet done ...
| Code: | Puzzle: FP041808
+-------+-------+-------+
| . . . | . . . | . . . |
| . . . | 7 . . | 5 . 8 |
| 6 5 . | . 3 2 | . 4 1 |
+-------+-------+-------+
| 2 . . | 1 . 3 | . . 6 |
| . . 1 | . . . | 8 . . |
| 7 . . | 4 . 6 | . . 2 |
+-------+-------+-------+
| 8 2 . | 5 1 . | . 9 4 |
| 3 . 9 | . . 8 | . . . |
| . . . | . . . | . . . |
+-------+-------+-------+ |
Keith |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Apr 19, 2008 1:38 pm Post subject: |
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After basics:
| Code: | +----------------+----------------+----------------+
| 19 348 2378 | 689 5 14 | 2679 236 39 |
| 19 34 23 | 7 69 14 | 5 236 8 |
| 6 5 78 | 89 3 2 | 79 4 1 |
+----------------+----------------+----------------+
| 2 89 58 | 1 789 3 | 4 57 6 |
| 4 6 1 | 29 279 5 | 8 37 39 |
| 7 389 358 | 4 89 6 | 19 15 2 |
+----------------+----------------+----------------+
| 8 2 6 | 5 1 7 | 3 9 4 |
| 3 7 9 | 26 4 8 | 126 126 5 |
| 5 1 4 | 3 26 9 | 26 8 7 |
+----------------+----------------+----------------+ |
Coloring (skyscrapers) eliminates some candidates <6>, and coloring on <9> solves R1C1 as <1>.
Which leads to here:
| Code: | +-------------+-------------+-------------+
| 1 38 27 | 89 5 4 | 27 6 39 |
| 9 4 23 | 7 6 1 | 5 23 8 |
| 6 5 78 | 89 3 2 | 79 4 1 |
+-------------+-------------+-------------+
| 2 89 58 | 1 789 3 | 4 57 6 |
| 4 6 1 | 2 79 5 | 8 37 39 |
| 7 389 358 | 4 89 6 | 19 15 2 |
+-------------+-------------+-------------+
| 8 2 6 | 5 1 7 | 3 9 4 |
| 3 7 9 | 6 4 8 | 12 12 5 |
| 5 1 4 | 3 2 9 | 6 8 7 |
+-------------+-------------+-------------+ |
Now, what? I believe this is not a BUG.
Keith |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Apr 19, 2008 1:47 pm Post subject: |
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Aha!
Two W-wings to attack <8> and <9> in R6C2, solving it as <3>.
Keith |
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Steve R
Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England
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| Posted: Sat Apr 19, 2008 2:49 pm Post subject: |
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You’ve given me my sort of solution so I’ll return the favour.
This is your first grid
| Code: | +----------------+----------------+----------------+
| 19 348 2378 | 689 5 14 | 2679 236 39 |
| 19 34 23 | 7 69 14 | 5 236 8 |
| 6 5 78 | 89 3 2 | 79 4 1 |
+----------------+----------------+----------------+
| 2 89+ 58 | 1 89+7 3 | 4 57 6 |
| 4 6 1 | 29 279 5 | 8 37 39 |
| 7 89+3 358 | 4 89+ 6 | 19 15 2 |
+----------------+----------------+----------------+
| 8 2 6 | 5 1 7 | 3 9 4 |
| 3 7 9 | 26 4 8 | 126 126 5 |
| 5 1 4 | 3 26 9 | 26 8 7 |
+----------------+----------------+----------------+ |
As r4c2 is conjugate to both r4c5 and r6c2 with respect to 9, placing 8 in it would immediately give a deadly pattern. So r4c2 contains 9.
This eliminates 9 from r6c2. But 8 can be eliminated as well because, if it does not contain 3, r4c5 contains 7, leaving r4c3 as the only place for 8 in row 4.
Strange reversal of roles!
Steve |
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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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| Posted: Sat Apr 19, 2008 3:07 pm Post subject: LA times |
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Two xy-chains also solve it. Brute strength!
Earl |
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Johan
Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium
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| Posted: Sat Apr 19, 2008 4:57 pm Post subject: |
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The [89]UR* in R46C25 pins digit <3> in R6C2, either R4C5=7 or/both R6C2=3 to avoid the 89 DP
R4C5=7 => R4C8=5 => R6C3=5 => R6C2=3
| Code: |
+-------------------------+-------------------------+-------------------------+
| 19 348 2378 | 689 5 14 | 2679 236 39 |
| 19 34 23 | 7 69 14 | 5 236 8 |
| 6 5 78 | 89 3 2 | 79 4 1 |
+-------------------------+-------------------------+-------------------------+
| 2 *89 58 | 1 *789 3 | 4 57 6 |
| 4 6 1 | 29 279 5 | 8 37 39 |
| 7 *389 358 | 4 *89 6 | 19 15 2 |
+-------------------------+-------------------------+-------------------------+
| 8 2 6 | 5 1 7 | 3 9 4 |
| 3 7 9 | 26 4 8 | 126 126 5 |
| 5 1 4 | 3 26 9 | 26 8 7 |
+-------------------------+-------------------------+-------------------------+ |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sat Apr 19, 2008 6:30 pm Post subject: |
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| Code: | +----------------+----------------+----------------+
| 19 348 2378 | 689 5 14 | 2679 236 39 |
| 19 34 23 | 7 69 14 | 5 236 8 |
| 6 5 #78 | 89 3 2 |#79 4 1 |
+----------------+----------------+----------------+
| 2 89 #58 | 1 789 3 | 4 57 6 |
| 4 6 1 | 29 279 5 | 8 37 39 |
| 7 389 358 | 4 89 6 |#19 #15 2 |
+----------------+----------------+----------------+
| 8 2 6 | 5 1 7 | 3 9 4 |
| 3 7 9 | 26 4 8 | 126 126 5 |
| 5 1 4 | 3 26 9 | 26 8 7 |
+----------------+----------------+----------------+ |
one xy-chain marked above from Ravel's after basics grid
r4c3 {58}-{78}-{79}-{19}-{15} ends in r6c8 removes 5 in r4c8 |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat Apr 19, 2008 9:12 pm Post subject: |
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| Same as Johan, breaking up the DP by removing 89 from r6c2 is all that's needed. |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Sat Apr 19, 2008 9:37 pm Post subject: |
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That 89 UR is certainly an efficient solution path! However, a comment: No "what if" references to surrounding cells is necessary to resolve this UR.
When a UR has diagonal bivalues and a UR digit is strongly linked on one side, that digit can be removed from the non-bivalue cell on the other side. (I believe I've seen this referred to as Type "6a" somewhere.)
Here, the rule is applied twice: (1) the strongly linked <9>s in c2 eliminate <9> from r4c5; (2) the strongly linked <8>s in c5 eliminate <8> from r6c2.
The logic should be fairly apparent. For instance, if r6c2 is <9>, r4c5 cannot be <9> due to the DP. If r6c2 is not <9>, r4c2 must be <9> due to the strong link. Either way, r4c5 cannot be <9>.
Having said all that, I didn't notice this UR and used the <9> Kite that pivots in b3 to remove <9> from r5c4. That led here:
| Code: | +-------------+------------+------------+
| 1 v38 27 | 89 5 4 | 27 6 p39 |
| 9 4 23 | 7 6 1 | 5 23 8 |
| 6 5 78 | 89 3 2 | 79 4 1 |
+-------------+------------+------------+
| 2 p89 58 | 1 789 3 | 4 57 6 |
| 4 6 1 | 2 79 5 | 8 37 39 |
| 7 #38-9 358 | 4 89 6 |t19 15 2 |
+-------------+------------+------------+
| 8 2 6 | 5 1 7 | 3 9 4 |
| 3 7 9 | 6 4 8 | 12 12 5 |
| 5 1 4 | 3 2 9 | 6 8 7 |
+-------------+------------+------------+ |
Since it pivots in r1c2, I immediately saw the "useless" XY Wing. The pincer at r1c9 is transported to r6c7, "t", eliminating <9> from r6c2, "#". This results in a BUG+1. |
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