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March 29 VH

 
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Clement



Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania

PostPosted: Sun Mar 28, 2010 11:36 pm    Post subject: March 29 VH Reply with quote

Four steps!
1) UR 89 eliminating 9 in r24c8
2) X-Wing in 9 r15c58 eliminating 9 in r5c4
3) X-Wing in 9 r24c49 eliminating 9's in r4c31
4) XY-Wing 46 49 69 eliminating 6's in r1c13 solving the puzzle.
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Sun Mar 28, 2010 11:58 pm    Post subject: Reply with quote

There is a single step:

XY wing <469>
r2c34 and r1c5 which takes out the 6 in r1c1.
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Mon Mar 29, 2010 1:27 am    Post subject: Reply with quote

I did not actually finish the puzzle, but I saw three moves which I thought might each finish it off. They were M-Wing (46), XY-Chain based on a UR (89) and XY-Wing (496).
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Mon Mar 29, 2010 4:32 pm    Post subject: Reply with quote

For those who don't like searching for xy/w/m-wings I found a path using mostly uniqueness....

Type-4 UR (89); r2c8<>9, r4c8<>9
Hidden Rectangle (26) apex at r3c8; r1c3<>6
x-wing (9); r5c4<>9
BUG+2 Either r3c3 or r1c8 = 6; r3c8<>6

Singles...
Multi-value Wings avoided...
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Clement



Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania

PostPosted: Mon Mar 29, 2010 5:57 pm    Post subject: March 29 VH Reply with quote

Yes, Mogulmeister & Marty,
XY-Wing (469) is a single steper. I missed some basic eliminations.
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Mon Mar 29, 2010 6:07 pm    Post subject: Reply with quote

..but that is what makes this game fun..some puzzles are made even more enjoyable as we go through our private arsenal of techniques and arrive at a solution.

An efficient single shot takedown isn't always nirvana. As in life, the journey is often better than the arriving.
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills

PostPosted: Mon Mar 29, 2010 11:45 pm    Post subject: Reply with quote

A couple of posts used the UR89 with the x-wing 8 overlay to eliminate 9 in r24c8.

However if we look at the implications inside the UR, we see another possibility. To prevent the deadly pattern, either r2c8=6 or r4c8=7. So, looking at these implications we get:
If r2c8=6, then r2c3=4, then r2c4=9.
If r4c8=7, then r5c8=9;
Thus r5c4<>9 so we have an additional deletion. Sorry to say, in the case that the additional deletion is not very helpful.

Ted
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Tue Mar 30, 2010 12:01 am    Post subject: Reply with quote

tlanglet wrote:
A couple of posts used the UR89 with the x-wing 8 overlay to eliminate 9 in r24c8.

However if we look at the implications inside the UR, we see another possibility. To prevent the deadly pattern, either r2c8=6 or r4c8=7. So, looking at these implications we get:
If r2c8=6, then r2c3=4, then r2c4=9.
If r4c8=7, then r5c8=9;
Thus r5c4<>9 so we have an additional deletion. Sorry to say, in the case that the additional deletion is not very helpful.

Ted

Ted,

I don't know if you saw my post about using the 89 UR as a basis for an XY-Chain. This was my grid after basics.

Code:

+-----------+----------+----------+
| 67 37 236 | 8   69 5 | 1 269 4  |
| 1  5  46  | 49  7  2 | 3 689 89 |
| 8  9  246 | 1   46 3 | 5 26  7  |
+-----------+----------+----------+
| 67 2  36  | 39  5  1 | 4 789 89 |
| 5  37 8   | 349 49 6 | 2 79  1  |
| 9  4  1   | 2   8  7 | 6 3   5  |
+-----------+----------+----------+
| 3  1  5   | 7   2  9 | 8 4   6  |
| 2  8  9   | 6   1  4 | 7 5   3  |
| 4  6  7   | 5   3  8 | 9 1   2  |
+-----------+----------+----------+

Play this puzzle online at the Daily Sudoku site

The DP killers have to be 6 in r2c8 or 7 in r4c8. If r2c8=6, then r1c1=7. Either way, r4c1<>7 and that's all that's needed.
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