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Clement
Joined: 24 Apr 2006
Posts: 1113
Location: Dar es Salaam Tanzania
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 Posted: Mon Nov 22, 2010 11:02 pm Post subject: Nov 23 VH |
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Three steps:-
1) UR 28 removes the 8's in BOX 7 row 8 opens
2) XY-Wing 58 25 28 removes 8 in r9c3 which opens onother
3) XY-Wing 58 57 78 eliminating 8 in r79c26 solves it. |
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kragzy
Joined: 01 May 2007
Posts: 112
Location: Australia
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| Posted: Tue Nov 23, 2010 1:20 am Post subject: |
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| Two steps for me: 258 XYZ wing centred on R8C3 which opens up a 578 XY wing centred on R9C3. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Tue Nov 23, 2010 4:39 am Post subject: |
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| A W-Wing on 78s in boxes 28, connected by 7s in c3, r7c6<>8, was enough. |
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George Woods
Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK
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| Posted: Tue Nov 23, 2010 11:42 am Post subject: er solution |
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the strongly linked 7 s in row 7 and col 6 deny a 7 in r2c6 since this would deny any 7 to box A
Last edited by George Woods on Wed Nov 24, 2010 1:48 pm; edited 1 time in total |
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yeoks
Joined: 16 May 2010
Posts: 33
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| Posted: Tue Nov 23, 2010 1:17 pm Post subject: |
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| A skyscraper (7) in columns 3 and 6 removes 7 from r7c1 and r9c4 and solves. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Tue Nov 23, 2010 3:10 pm Post subject: |
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Simple coloring on 7 is also a one step solution.
Another one step solution that may be of interest to some because it is a little different than the standard moves is an "almost or finned" xy-wing 5-78 with vertex (58)r7c2, pincers (78)r7c6 & (57)r9c3 plus the fin (8)r9c3.
Code after basics:
| Code: |
*-----------------------------------------------------------*
| 78 4 3 | 2 9 5 | 78 1 6 |
| 5 168 178 | 678 4 78 | 3 9 2 |
| 678 2 9 | 678 1 3 | 578 578 4 |
|-------------------+-------------------+-------------------|
| 28 3 28 | 1 7 6 | 9 4 5 |
| 9 15 15 | 3 2 4 | 67 67 8 |
| 4 7 6 | 5 8 9 | 1 2 3 |
|-------------------+-------------------+-------------------|
| 38-7 *58 4 | 9 6 *78 | 2 358 1 |
| 2368 9 258 | 4 35 1 | 568 3568 7 |
| 1 568 *57(8) | 78 35 2 | 4 3568 9 |
*-----------------------------------------------------------* |
Either the xy-wing is true (r9c3<>8) or the fin is true (r9c3=8)
If the xy-wing is true then the two pincers on 7 in r7c6 & r9c3 eliminate the 7 in r7c1;
If the fin in true then r9c3=8, r4c3<>8, then r4c1=8, then r1c1<>8=7 which eliminates the 7 in r7c1:
Thus, r7c1<>7 to complete the puzzle.
Ted |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Tue Nov 23, 2010 5:39 pm Post subject: Re: er solution |
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| George Woods wrote: | | the strongly linked 7 s in row 7 and col 6 deny a 6 in r2c6 since this would deny any 7 to box A |
George, I could have screwed up, but my basics had solved r4c6=6 |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Tue Nov 23, 2010 6:06 pm Post subject: |
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This is my post-basics grid:
| Code: |
+--------------+-----------+------------+
| 78 4 3 | 2 9 5 | 78 1 6 |
| 5 168 178 | 678 4 78 | 3 9 2 |
| 678 2 9 | 678 1 3 | 578 578 4 |
+--------------+-----------+------------+
| 28 3 28 | 1 7 6 | 9 4 5 |
| 9 15 15 | 3 2 4 | 67 67 8 |
| 4 7 6 | 5 8 9 | 1 2 3 |
+--------------+-----------+------------+
| 378 58 4 | 9 6 78 | 2 358 1 |
| 2368 9 258 | 4 35 1 | 568 3568 7 |
| 1 568 578 | 78 35 2 | 4 3568 9 |
+--------------+-----------+------------+
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Play this puzzle online at the Daily Sudoku site |
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prakash
Joined: 02 Jan 2008
Posts: 67
Location: New Jersey, USA
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| Posted: Wed Nov 24, 2010 2:35 am Post subject: |
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| A finned X wing on 7s provides elimination similar to the skyscraper on 7. |
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George Woods
Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK
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| Posted: Wed Nov 24, 2010 10:15 am Post subject: er in A |
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marty wrote
George, I could have screwed up, but my basics had solved r4c6=6
My original said "deny a 6", but of course I should have written "deny a 7"
Sorry |
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Ema Nymton
Joined: 17 Apr 2009
Posts: 89
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| Posted: Fri Nov 26, 2010 10:57 am Post subject: |
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.
Basic has arrived here:
| Code: |
+--------------+-----------+------------+
| 78 4 3 | 2 9 5 | 78 1 6 |
| 5 168 178 | 678 4 78 | 3 9 2 |
| 678 2 9 | 678 1 3 | 578 578 4 |
+--------------+-----------+------------+
| 28 3 28 | 1 7 6 | 9 4 5 |
| 9 15 15 | 3 2 4 | 67 67 8 |
| 4 7 6 | 5 8 9 | 1 2 3 |
+--------------+-----------+------------+
| 378* 58 4 | 9 6 78 | 2 358 1 |
| 2368 9 258 | 4 35 1 | 568 3568 7 |
| 1 568 578 | 78 35 2 | 4 3568 9 |
+--------------+-----------+------------+
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Draw/Play gives as Hint - r7c1 is '3'. Is it possible one can explain why?
Still trying to follow the reasoning of the puzzler.
Ema Nymton
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Fri Nov 26, 2010 5:23 pm Post subject: |
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Ema,
Form the position you posted there is an XYZ-wing 25-8 and then an XY-wing 5-78 that solve R7C2 as 8 and then R7C1 as 3.
Sudoku Susser is a very good tool to explain moves.
Best wishes,
Keith |
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jLo
Joined: 30 Apr 2007
Posts: 55
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| Posted: Sat Nov 27, 2010 11:16 pm Post subject: |
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Regarding the Draw/Play hint of 3 at r7c1.
From the posted position,
| Code: |
+--------------+-----------+------------+
| 78 4 3 | 2 9 5 | 78 1 6 |
| 5 168 178 | 678 4 78 | 3 9 2 |
| 678 2 9 | 678 1 3 | 578 578 4 |
+--------------+-----------+------------+
| 28 3 28 | 1 7 6 | 9 4 5 |
| 9 15 15 | 3 2 4 | 67 67 8 |
| 4 7 6 | 5 8 9 | 1 2 3 |
+--------------+-----------+------------+
| 378* 58 4 | 9 6 78 | 2 358 1 |
| 2368 9 258 | 4 35 1 | 568 3568 7 |
| 1 568 578 | 78 35 2 | 4 3568 9 |
+--------------+-----------+------------+
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There is a finned X-wing on 8's in columns 2 and 6 that eliminates
8 from R7C1 but produces no additional simple eliminations.
Follow that with an almost identical finned X-wing on 7's in columns
3 and 6 that eliminates 7 from R7C1, leaving you with R7C1=3. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sun Nov 28, 2010 4:46 am Post subject: |
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The conundrum is that draw/play supposedly only understands X-wings, XY-wings, and XYZ-wings as advanced moves.
With only those tools in the toolbox, I see no direct way from Ema's grid to R7C1 <3>.
Keith |
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