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feb 22 vh

 
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Fri Feb 22, 2008 5:09 am    Post subject: feb 22 vh Reply with quote

well its midnight here on the east coast, USA. that also means that Nataraj will be here shortly to see the new VH posted, haha Smile

put me down for multicoloring on 2.
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Fri Feb 22, 2008 11:50 am    Post subject: Reply with quote

How well you know me, Norm ...

but last night I was online past midnight and indeed could have had a go at today's but I was busy elsewhere. Today I took a day off and spent the morning without my usual sudoku breakfast. So here goes at noon:

(Multi)Coloring on 2 yielded a rich crop, that's right. Then at some point I spotted an xy-wing (39-23-29) which solved r6c2=9 and the puzzle.

____

edit 1450 CET (1350 UTC): apparently I did not harvest ALL the crop from coloring on 2 when I did the puzzle on paper. My computer showed me a few more of those coloring eliminations and the xy-wing was not necessary.

After basics:
Code:


+--------------------------+--------------------------+--------------------------+
| 23569   239     235      | 1       2367    2367     | 28      58      4        |
| 256     1       7        | 8       26      4        | 3       9       25       |
| 23      4       8        | 5       23      9        | 1       6       7        |
+--------------------------+--------------------------+--------------------------+
| 237     8       6        | 4       5       23       | 9       37      1        |
| 2379    5       23       | 29      23689   1        | 78      4       368      |
| 4       39      1        | 7       3689    36       | 5       2       368      |
+--------------------------+--------------------------+--------------------------+
| 1       23      235      | 6       279     27       | 4       58      89       |
| 25      7       9        | 3       4       8        | 6       1       25       |
| 8       6       4        | 29      1       5        | 27      37      39       |
+--------------------------+--------------------------+--------------------------+


"2" is present at many places and forms many nice strong links:
Code:

+·····+·····+·····+
·o * o·  o o·*    ·
·  |  ·     ·|\-\ ·
·o |  ·  o  ·|   *·
·  |  ·     ·|   |·
·*-------*  ·|   |·
+··|··+·····+|···|+
·*---------*·|   |·
·  |  ·     ·|   |·
·o | o·* o  ·|   |·
·  |  ·|    ·|   |·
·  |  ·|    ·|   |·
+··|··+|····+|···|+
·  * o·| o o·|   |·
·     ·|    ·|   |·
·*---------------*·
·     ·|    ·|/-/ ·
·     ·*-----*    ·
+·····+·····+·····+

2 can be removed from 12 cells (unbelievable, when I first did it, i made 3 - three!- eliminations only and thought that was a lot!):

r1c1, r1c3, r1c5, r1c6, r2c9, r5c4, r5c5, r7c3, r7c5, r7c6, r8c1, r9c7
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Fri Feb 22, 2008 2:08 pm    Post subject: Reply with quote

alternatively (and for the more wing-inclined Smile ) the xy-wing solves the puzzle, too. No coloring needed. Seems like by not being thorough enough I found two solutions in one try. Very Happy
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Johan



Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium

PostPosted: Fri Feb 22, 2008 4:01 pm    Post subject: Reply with quote

For those who want to take advantage of possible UR's present in the grid.
A "very" alternative way(which is an understatement)to complete this VH is a full dissection of the possible [68] UR* in R56C59 that takes out <2> in R9C7 solving the puzzle. Four ways to avoid the [68] DP.

1. R5C5=2 => R5C4=9 => R9C4=2(A)
2. R56C5=3 => R4C6=2 => R5C4=9 => R9C4=2(A)
3. R56C5=9 => R5C4=2 => R4C6=3 => R4C8=7 => R5C7=8 => R1C7=2(B)
4. R56C9=3 => R4C8=7 => R5C7=8 => R1C7=2(B)

Code:
+------------------------+------------------------+------------------------+
| 23569     239     235  | 1       2367      2367 | 28 B      58      4    |
| 256       1       7    | 8       26        4    | 3         9       25   |
| 23        4       8    | 5       23        9    | 1         6       7    |
+------------------------+------------------------+------------------------+
| 237       8       6    | 4       5         23   | 9         37      1    |
| 2379      5       23   | 29    * 23689     1    | 78        4     * 368  |
| 4         39      1    | 7     * 3689      36   | 5         2     * 368  |
+------------------------+------------------------+------------------------+
| 1         23      235  | 6       279       27   | 4         58      89   |
| 25        7       9    | 3       4         8    | 6         1       25   |
| 8         6       4    | 29 A    1         5    |-[2]7      37      39   |
+------------------------+------------------------+------------------------+
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Marty R.



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

PostPosted: Fri Feb 22, 2008 4:27 pm    Post subject: Reply with quote

I'm sure I missed a few things, because it took me more steps than it should have. There was a skyscraper, Finned X-Wing, couple of simple colorings and a multi-coloring before I spotted a 25-23-35 XY-Wing which solved it.
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sdq_pete



Joined: 30 Apr 2007
Posts: 119
Location: Rotterdam, NL

PostPosted: Fri Feb 22, 2008 9:05 pm    Post subject: Reply with quote

Er, which 35 was that Marty? I had XY 23-29-39 (pivot 23 at R5C3).
Peter
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Fri Feb 22, 2008 9:34 pm    Post subject: Reply with quote

just like to add that there are many fish present in the grid after basics as well. many fish on 2 and an x-wing on 5.

the x-wing on 5 does not solve the puzzle, at least from what I could tell.
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Marty R.



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

PostPosted: Fri Feb 22, 2008 10:08 pm    Post subject: Reply with quote

sdq_pete wrote:
Er, which 35 was that Marty? I had XY 23-29-39 (pivot 23 at R5C3).
Peter

Pete,

I'm pretty sure it was pivoted in r8c2 and took out a 5 from r1c3. I had done two simple colorings and one multi-coloring on 2 and my grid had fewer 2s than Johan's grid above.
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George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Sun Feb 24, 2008 12:18 am    Post subject: another maverik? Reply with quote

For my solution I observed that a 2 in col1 of block 4 is disastrous, because consequent 2s in row 1 of block 1 and r8c9 deny a 2 in block 3. i.e. it is like an "ER". Anyway this gives a 2 in r5c3 and that solves it!
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scoller



Joined: 24 Feb 2008
Posts: 1

PostPosted: Sun Feb 24, 2008 7:28 pm    Post subject: Reply with quote

simple newbie solution

UR on 25 makes R2C1 = 6, therefore R2C5 = 2 and that solves the puzzle
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Marty R.



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

PostPosted: Sun Feb 24, 2008 10:10 pm    Post subject: Reply with quote

scoller wrote:
simple newbie solution

UR on 25 makes R2C1 = 6, therefore R2C5 = 2 and that solves the puzzle

Scoller, welcome to the forum.

I'm not seeing a UR, at least in the grid in Johan's post. If you're using the 25 cells in boxes 3, 7 and 9, it's not valid to remove the 25 from r2c1 because UR logic applies only when the four corners are confined to two boxes.

Perhaps you were looking at a different grid?
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Victor



Joined: 29 Sep 2005
Posts: 207
Location: NI

PostPosted: Sun Feb 24, 2008 10:31 pm    Post subject: Reply with quote

Splendid from Johan as usual. A really nice solution from George: I love bouncing ER-type stuff like this!
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