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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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 Posted: Sun Aug 31, 2008 2:42 am Post subject: 8-29 competition |
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| Code: | . . 3|. . .|. 4 .
. 1 .|6 4 .|. . .
. . .|1 . 8|7 . 2
-----+-----+-----
. 8 7|. . .|2 . .
9 . .|. 2 .|. . 5
. . 2|. . .|1 6 .
-----+-----+-----
3 . 1|9 . 4|. . .
. . .|. 6 5|. 1 .
. 9 .|. . .|8 . . |
| Code: | .------------------.------------------.------------------.
| 8 27 3 | 5 79 279 | 6 4 1 |
| 27 1 59 | 6 4 27 | 39 3589 389 |
| 456 456 4569 | 1 3 8 | 7 59 2 |
:------------------+------------------+------------------:
| 1 8 7 | 34 5 6 | 2 39 349 |
| 9 346 46 | 78 2 1 | 34 78 5 |
| 45 345 2 | 3478 79 379 | 1 6 78 |
:------------------+------------------+------------------:
| 3 267 1 | 9 8 4 | 5 27 67 |
| 27 247 8 | 237 6 5 | 349 1 3479 |
| 456 9 456 | 237 1 37 | 8 237 46 |
'------------------'------------------'------------------' |
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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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| Posted: Sun Aug 31, 2008 3:15 am Post subject: challenge |
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An xy-chain eliminates the 2 in R7C2, which leads to coloring (7) to solve the puzzle.
Earl |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sun Aug 31, 2008 7:39 am Post subject: |
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I'll add this one from the telegraph, for friday the 29th. it can also be solved in the same manner.
| Code: | . . .|. 6 .|3 . .
. . 6|. 4 .|. 1 8
. . 5|. . .|7 . .
-----+-----+-----
. 9 .|2 8 .|. . .
. . 4|. . .|. . .
. . .|. 5 7|. 6 .
-----+-----+-----
. 4 1|. . .|9 . .
6 2 .|. 9 .|5 . .
3 . 9|. . .|. . . |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Sun Aug 31, 2008 12:03 pm Post subject: Re: challenge |
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| Earl wrote: | | An xy-chain eliminates the 2 in R7C2 |
A very long one.
| Code: | *-----------------------------------------------------------*
| 8 #27 3 | 5 79 29 | 6 4 1 |
|*27 1 59 | 6 4 #27 | 39 3589 389 |
| 456 456 4569 | 1 3 8 | 7 59 2 |
|-------------------+-------------------+-------------------|
| 1 8 7 | 34 5 6 | 2 39 349 |
| 9 346 46 |@78 2 1 | 34 @78 5 |
| 45 345 2 | 3478 79 39 | 1 6 78 |
|-------------------+-------------------+-------------------|
| 3 -267 1 | 9 8 4 | 5 #27 67 |
| 27 247 8 | 23 6 5 | 349 1 3479 |
| 456 9 456 |@237 1 @37 | 8 23 46 |
*-----------------------------------------------------------*
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An alternative for the same elimination is the w-wing 27 in r2c6/r7c8 connected by the skyscraper for 7 in rows 59.
The 2 in r2c6 easlily transports to the 2 in r1c2.
The second puzzle only neds an extended xy-wing (aka generalized/grouped xy-wing or 4-cell-xy-chain). |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Sun Aug 31, 2008 4:03 pm Post subject: Re: challenge |
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| ravel wrote: | | A very long one. |
Is the XY-Chain really all that long? Besides, it's also a generalized Remote Naked Pair linking <27> cells via <7>.
| Code: | -2r1c2 7r1c2 -7r1c5 7r6c5 -7r5c4 7r5c8 -7r7c8 2r7c8 => [r7c2]<>2
+--------------------------------------------------------------+
| 8 *27 3 | 5 *79 279 | 6 4 1 |
| 27 1 59 | 6 4 27 | 39 3589 389 |
| 456 456 4569 | 1 3 8 | 7 59 2 |
|--------------------+--------------------+--------------------|
| 1 8 7 | 34 5 6 | 2 39 349 |
| 9 346 46 | *78 2 1 | 34 *78 5 |
| 45 345 2 | 3478 *79 379 | 1 6 78 |
|--------------------+--------------------+--------------------|
| 3 267 1 | 9 8 4 | 5 *27 67 |
| 27 247 8 | 23 6 5 | 349 1 3479 |
| 456 9 456 | 237 1 37 | 8 23 46 |
+--------------------------------------------------------------+
# 63 eliminations remain
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Note: I don't normally list the internal eliminations. So don't get spoiled  |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Mon Sep 01, 2008 12:14 am Post subject: |
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Danny,
I'm not sure about the Remote Naked Pair, but r1c2 and r7c8 are certainly a Semi-RNP (aka W-Wing) activated by the 7 Kite that pivots in box 5, as you've marked it... eliminating the need for ravel's "transport". |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Mon Sep 01, 2008 6:38 am Post subject: |
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| Code: | 6 2 .|5 . .|1 . .
. . .|. . .|. 4 6
4 7 .|6 . 1|. . .
-----+-----+-----
. . .|8 . .|. 6 .
5 . 6|. . .|7 . 9
. 4 .|. . 9|. . .
-----+-----+-----
. . .|. . 8|. 3 1
7 8 .|. . .|. . .
. . 2|. . .|. . 5 |
this is the sunday competition. doesn't need xy-chains this time. |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Mon Sep 01, 2008 10:05 am Post subject: Re: challenge |
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| daj95376 wrote: | | Is the XY-Chain really all that long? |
The one i found had 8 cells (from r8c1 to r7c8). Thats the problem i have with xy-chains. There are so much possibilities, that even when you know, that there is one, you will not always find the shortest one first.
But ok, i also missed the kite-w-wing, because i saw the skyscraper-w-wing first  |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Mon Sep 01, 2008 3:53 pm Post subject: |
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| Asellus wrote: | Danny,
I'm not sure about the Remote Naked Pair, but r1c2 and r7c8 are certainly a Semi-RNP (aka W-Wing) activated by the 7 Kite that pivots in box 5, as you've marked it... eliminating the need for ravel's "transport". |
| I wrote: | generalized Remote Naked Pair
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keith calls it a General Remote Pair in (E) below. I reworded it slightly. A Semi-RNP works for me as well. In fact, it's also been called a Y-Wing Styles, but that created lots of confusion with people shortening it to Y-Wing, so I stay away from using it.
http://www.dailysudoku.com/sudoku/forums/viewtopic.php?p=9097&sid=7a26270a8dc247c7ac3a256634efa790#9097 |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Mon Sep 01, 2008 4:37 pm Post subject: |
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| daj95376 wrote: | | Asellus wrote: | Danny,
I'm not sure about the Remote Naked Pair, but r1c2 and r7c8 are certainly a Semi-RNP (aka W-Wing) activated by the 7 Kite that pivots in box 5, as you've marked it... eliminating the need for ravel's "transport". |
| I wrote: | generalized Remote Naked Pair
|
keith calls it a General Remote Pair in (E) below. I reworded it slightly. A Semi-RNP works for me as well. It's also been called a Y-Wing Styles, but that created lots of confusion with people shortening it to Y-Wing, so I stay away from using it.
http://www.dailysudoku.com/sudoku/forums/viewtopic.php?p=9097&sid=7a26270a8dc247c7ac3a256634efa790#9097 |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Tue Sep 02, 2008 3:20 am Post subject: |
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Danny,
I have to disagree: As far as I can see, and based on your asterisk markings, your 27 pair is not what Keith was describing as a General Remote (Naked) Pair. He describes a pair that is connected by an odd number of strong (by which he means conjugate) links in one of the digits such that the two instances of that digit (and thus of both digits) of the remote pair are conjugate with each other. Your chain of <7> links contains a weak link in box 5. Thus, a weak inference link (not a conjugate, let alone a strong, link) is induced between the <7>s in the remote 27 pair. In turn, this induces a strong inference between the <2>s (ie, W-Wing). However, it is possible that both cells are <2>, which is not a RNP in my book.... only "half" of one.
Perhaps "generalized RNP" has some meaning in the Players' Forum beyond what Keith was describing. But, quite a bit of the lingo in that forum is an alien tongue in this forum. |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Tue Sep 02, 2008 4:09 am Post subject: |
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| Asellus wrote: | | I have to disagree |
I concede the point. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Tue Sep 02, 2008 4:58 am Post subject: |
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Thge way I see it is this. Ignoring the UR: | Code: | +----------------+----------------+----------------+
| 8 27c 3 | 5 79B 279 | 6 4 1 |
| 27 1 59 | 6 4 27 | 39 3589 389 |
| 456 456 4569 | 1 3 8 | 7 59 2 |
+----------------+----------------+----------------+
| 1 8 7 | 34 5 6 | 2 39 349 |
| 9 346 46 | 78a 2 1 | 34 78A 5 |
| 45 345 2 | 3478 79b 379 | 1 6 78 |
+----------------+----------------+----------------+
| 3 -267 1 | 9 8 4 | 5 27C 67 |
| 27 247 8 | 23 6 5 | 349 1 3479 |
| 456 9 456 | 237 1 37 | 8 23 46 |
+----------------+----------------+----------------+ |
aA and bB are a kite (turbot fish, whatever). Any cell that sees both A and B cannot be <7>. One, or both, of A and B are <7>. Therefore, one or both of c and C are <2>. R6C2 cannot be <2>. Which solves the puzzle.
However, in the solution, R7C2 is <6>. It is not <27>. Is there an argument that says cC are indeed a remote pair? (Any cell that sees both of them is not <27>.) Or, a separate chain that eliminates <7> from R7C2?
Keith |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Tue Sep 02, 2008 1:46 pm Post subject: |
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| keith wrote: | Or, a separate chain that eliminates <7> from R7C2?
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I did not find a basic chain. However, there is a SIN for the elimination.
| Code: | SIN: 7r7c2 7r5c8 8r2c8 5r2c3 5r9c1 6r9c3 [b4]~4 => [r7c2]<>7
state after SIN
*-----------------------------------------------------------*
| 8 2 3 | 5 79 279 | 6 4 1 |
| 27 1 d5 | 6 4 27 | 39 c8 39 |
| 46 46 49 | 1 3 8 | 7 59 2 |
|-------------------+-------------------+-------------------|
| 1 8 7 | 34 5 6 | 2 39 349 |
| 9 346 #4 | 8 2 1 | 34 b7 5 |
|#4 345 2 | 3478 79 379 | 1 6 8 |
|-------------------+-------------------+-------------------|
| 3 a7 1 | 9 8 4 | 5 2 6 |
| 2 24 8 | 23 6 5 | 349 1 3479 |
|e5 9 f6 | 237 1 37 | 8 23 4 |
*-----------------------------------------------------------*
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Wed Sep 03, 2008 1:36 am Post subject: |
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| keith wrote: | | However, in the solution, R7C2 is <6>. It is not <27>. Is there an argument that says cC are indeed a remote pair? |
If, as you say, r7c2 is <6> in the solution, then it is impossible to demonstrate that r1c2 and r7c8 are a RNP because they must both be <2> in the solution. Anything that claimed to show a conjugate RNP relationship between these cells would be in error.
Danny,
I'm glad to hear that we don't have some confusing clash of terminology and that this was just an inapt example. Thanks for clarifying. |
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