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crunched
Joined: 05 Feb 2008
Posts: 168
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 Posted: Sat Sep 27, 2008 7:34 am Post subject: Sept 27 vh |
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I tried this 3 times and solved it 3 different ways. I found 2 x wings and 2 xy wings.
| Code: |
+-------------+----------+---------------+
| 678 3 1 | 2 4 58 | 5678 678 9 |
| 678 5 678 | 9 3 18 | 2 4 167 |
| 4 9 2 | 6 7 158 | 158 18 3 |
+-------------+----------+---------------+
| 9 16 3 | 5 8 2 | 4 167 167 |
| 168 7 68 | 4 9 3 | 16 5 2 |
| 2 4 5 | 1 6 7 | 9 3 8 |
+-------------+----------+---------------+
| 3 68 9 | 78 1 4 | 678 2 5 |
| 178 2 4 | 3 5 6 | 178 9 17 |
| 5 168 678 | 78 2 9 | 3 1678 4 |
+-------------+----------+---------------+
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Play this puzzle online at the Daily Sudoku site |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sat Sep 27, 2008 9:22 am Post subject: |
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The grid can be further reduced (8 in box 7 confined to col 2, and resulting cleanup) to
| Code: |
+--------------------------+--------------------------+--------------------------+
| 678 3 1 | 2 4 58 | 567 678 9 |
| 678 5 678 | 9 3 18 | 2 4 167 |
| 4 9 2 | 6 7 158 | 15 18 3 |
+--------------------------+--------------------------+--------------------------+
| 9 16 3 | 5 8 2 | 4 167 167 |
| 168 7 68 | 4 9 3 | 16 5 2 |
| 2 4 5 | 1 6 7 | 9 3 8 |
+--------------------------+--------------------------+--------------------------+
| 3 68 9 | 78 1 4 | 67 2 5 |
| 17 2 4 | 3 5 6 | 8 9 17 |
| 5 168 67 | 78 2 9 | 3 167 4 |
+--------------------------+--------------------------+--------------------------+
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There is now an xy-wing 67-68-78 in boxes 7 and 8
and another one 16-67-17 in boxes 6 and 9.
No x-wing as far as I can see, but some other colorful options. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat Sep 27, 2008 11:28 am Post subject: |
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| Quote: | | The grid can be further reduced (8 in box 7 confined to col 2, and resulting cleanup) |
Didn't understand that - can't see any further reductions from Crunched's grid. (Crunched's doesn't sound right)
But there is an x-wing on <1> (C17) which gives a one-step solution.
And another with an ER on <6>. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Sat Sep 27, 2008 11:44 am Post subject: |
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| nataraj wrote: | The grid can be further reduced (8 in box 7 confined to col 2, and resulting cleanup) to
| Code: |
+--------------------------+--------------------------+--------------------------+
| 678 3 1 | 2 4 58 | 567 678 9 |
| 678 5 678 | 9 3 18 | 2 4 167 |
| 4 9 2 | 6 7 158 | 15 18 3 |
+--------------------------+--------------------------+--------------------------+
| 9 16 3 | 5 8 2 | 4 167 167 |
| 168 7 68 | 4 9 3 | 16 5 2 |
| 2 4 5 | 1 6 7 | 9 3 8 |
+--------------------------+--------------------------+--------------------------+
| 3 68 9 | 78 1 4 | 67 2 5 |
| 17 2 4 | 3 5 6 | 8 9 17 |
| 5 168 67 | 78 2 9 | 3 167 4 |
+--------------------------+--------------------------+--------------------------+
|
There is now an xy-wing 67-68-78 in boxes 7 and 8
and another one 16-67-17 in boxes 6 and 9.
No x-wing as far as I can see, but some other colorful options. |
In fact Nataraj, I believe that two xy-wings <678> exist in boxes 7 and 8; the one you noted with pivot <68> at r7c2 and another with pivot <67> at r9c3. Both finish the puzzle.
Also, a x-wing <1> opens up after the xy-wing <167> that you also noted, but I fail to see any immediately after basics.
Ted |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Sat Sep 27, 2008 11:55 am Post subject: |
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| cgordon wrote: | | Quote: | | The grid can be further reduced (8 in box 7 confined to col 2, and resulting cleanup) |
Didn't understand that - can't see any further reductions from Crunched's grid. (Crunched's doesn't sound right)
But there is an x-wing on <1> (C17) which gives a one-step solution.
And another with an ER on <6>. |
Craig, all of the candidate digit <8> for col 2 reside in box 7, thus the two additional <8s> in box <7>, r8c1 & r9c3, can be eliminated as noted by Nataraj.
Also, when I look at the code posted by "crunched", I see a <1> in r3c7, which invalidates the x-wing you noted.
Ted |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sat Sep 27, 2008 12:01 pm Post subject: |
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| cgordon wrote: | | Quote: | | The grid can be further reduced (8 in box 7 confined to col 2, and resulting cleanup) |
Didn't understand that - can't see any further reductions from Crunched's grid. |
Craig,
8 in column 2 is confined to two cells: r7c2 and r9c2.
Therefore, in crunched's grid, 8 is not a candidate in r8c1 and r9c3. This is called a box-line interaction and usually is regarded as one of the basic techniques. This is why I said "...can be further reduced".
With 8 gone from r8c1, the naked pair 17 in r8c19 leaves 8 as a naked single in r8c7 and I definitely see no x-wing (1) in cols 1 and 7.
@tlanglet: Quite right, Ted! There are two overlapping xy-wings, one eliminating 7 and one eliminating 8 from the pair in r79c7. After the xy-wing I went on to solve the puzzle without more advanced moves (at least not that I remember). It is quite possible that there are any number of x-wings or even more exotic creatures, I just did not look for them. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat Sep 27, 2008 12:13 pm Post subject: |
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| Ted/Nataraj: Yes - I see the <8> elimination now - I have difficulty spotting those things. And there is no x-wing - that was merely Friday night/Saturday morning brain damage. But eh !! There was an ER on <6> |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sat Sep 27, 2008 12:37 pm Post subject: |
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| cgordon wrote: | | Ted/Nataraj: Yes - I see the <8> elimination now - I have difficulty spotting those things. And there is no x-wing - that was merely Friday night/Saturday morning brain damage. But eh !! There was an ER on <6> |
the ER is there for sure:
Box 4 together with strong link (6) in row7 make r5c7=1.
Now that I look at the grid more closely, there is also a
w-wing(6) r7c7=r9c3 via strong link on 7 in col 4 and it removes 6 from r7c2 and r9c8 |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat Sep 27, 2008 3:56 pm Post subject: |
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| Let me redeem myself. With the removal of the <8>s in Box 7 we are left with an x wing on <8>. Doesn't do much - but that's not the point. |
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Clement
Joined: 24 Apr 2006
Posts: 1113
Location: Dar es Salaam Tanzania
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| Posted: Sat Sep 27, 2008 6:04 pm Post subject: Daily Sudoku: Sat 27-Sep-2008 VH |
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XY-Wing (678) Pivot in r7c2 with candidates {6,8} eliminating 7 in r9c4 solves the puzzle.  |
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Clement
Joined: 24 Apr 2006
Posts: 1113
Location: Dar es Salaam Tanzania
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| Posted: Sat Sep 27, 2008 7:15 pm Post subject: |
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| XY-Wing (678) Pivot in r7c2 {6,8} eliminating 7 in r9c4 solves the puzzle. |
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crunched
Joined: 05 Feb 2008
Posts: 168
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| Posted: Sat Sep 27, 2008 7:43 pm Post subject: |
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If one never noticed the 8 reduction in Box 7 (that would include me) then an 8 wing in columns 2, 4 does much. It removes several 8s and helps open up the xy wing which wins the derby.
| cgordon wrote: | | Let me redeem myself. With the removal of the <8>s in Box 7 we are left with an x wing on <8>. Doesn't do much - but that's not the point. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Sep 27, 2008 8:48 pm Post subject: |
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 I am amazed to see that a basic move destroys a Wing which solves the puzzle. I got to here: | Code: | +----------------+----------------+----------------+
| 678 3 1 | 2 4 58 | 5678 678 9 |
| 678 5 678 | 9 3 18 | 2 4 167 |
| 4 9 2 | 6 7 158 | 158 18 3 |
+----------------+----------------+----------------+
| 9 16 3 | 5 8 2 | 4 167 167 |
| 168 7 68 | 4 9 3 | 16 5 2 |
| 2 4 5 | 1 6 7 | 9 3 8 |
+----------------+----------------+----------------+
| 3 68@ 9 | 78 1 4 | 678 2 5 |
| 178 2 4 | 3 5 6 | 178 9 17 |
| 5 16-8 678@ | 78@ 2 9 | 3 1678 4 |
+----------------+----------------+----------------+ |
There is an XYZ-wing <678> that takes out <8> in R9C2 and solves the puzzle in one step.
I did not notice the elimination of <8> in B7C13 as discussed above!
Keith
(I do see now that the XYZ-wing becomes an XY-wing, making the same elimination.) |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat Sep 27, 2008 9:25 pm Post subject: |
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| My one step was a W-Wing on 67. I don't see any grids here that offer the possibility, so I probably missed something that others caught. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sat Sep 27, 2008 10:12 pm Post subject: |
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Marty, my grid "after basics" above does indeed offer the possibility
| nataraj wrote: | Now that I look at the grid more closely, there is also a
w-wing(6) r7c7=r9c3 via strong link on 7 in col 4 and it removes 6 from r7c2 and r9c8 |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Sep 28, 2008 12:05 am Post subject: |
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| nataraj wrote: | Marty, my grid "after basics" above does indeed offer the possibility
| nataraj wrote: | Now that I look at the grid more closely, there is also a
w-wing(6) r7c7=r9c3 via strong link on 7 in col 4 and it removes 6 from r7c2 and r9c8 |
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It does indeed, but I'm thinking mine was in boxes 13. At any rate, if that is correct, I couldn't replicate the situation when I tried it a second time, this time online. |
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