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Another one for Marty

 
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keith



Joined: 19 Sep 2005
Posts: 3165
Location: near Detroit, Michigan, USA

PostPosted: Mon Aug 28, 2006 10:45 pm    Post subject: Another one for Marty Reply with quote

Here is another one, this time from the Daily Telegraph.
Puzzle: DT081106 Diabolical
Code:
+-------+-------+-------+
| . . 8 | . . 4 | . 1 . |
| . . 3 | . 9 . | . . . |
| 7 . . | 1 . . | . . . |
+-------+-------+-------+
| . . 7 | 5 . 2 | . 6 4 |
| 2 . . | 6 . 9 | . . 8 |
| 8 6 . | 4 . 7 | 2 . . |
+-------+-------+-------+
| . . . | . . 5 | . . 7 |
| . . . | . 6 . | 8 . . |
| . 3 . | 7 . . | 4 . . |
+-------+-------+-------+
Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5158
Location: Rochester, NY, USA

PostPosted: Tue Aug 29, 2006 5:10 am    Post subject: Reply with quote

What did I do to deserve being the recipient of this gift? Laughing

I enjoyed doing it, but I couldn't find any strong links to use, which is why I thought you directed it to me. There were also a few "almost" rectangles that I couldn't do anything with.

There were two finned X-Wings, an XYZ-Wing, an XY-Wing and a removal of a candidate to break up a deadly pattern, but all of these moves were of minimum to only moderate value. Finally, I noticed a second XY-Wing and this broke things open.

A fun puzzle because it used a variety of techniques and I didn't have to resort to chains.
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keith



Joined: 19 Sep 2005
Posts: 3165
Location: near Detroit, Michigan, USA

PostPosted: Tue Aug 29, 2006 9:34 pm    Post subject: Forked again! Reply with quote

Marty,

When I solved the puzzle, it came to a sticking point where there were two XY-wings (as I recall). Then it opened up for a few moves.

The final thing that solved the puzzle though, was a fork on <9>.

I'll post the details later.

Keith
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keith



Joined: 19 Sep 2005
Posts: 3165
Location: near Detroit, Michigan, USA

PostPosted: Wed Aug 30, 2006 5:32 pm    Post subject: Solving the puzzle Reply with quote

This is quite an interesting puzzle. Sudoku Susser says it needs:

3 x Simple Forcing Chains
1 x Simple Forcing Loops
3 x XYZ-Wing
1 x XY-Wing
4 x Intersection Removal
2 x Simple Hidden Sets
1 x Simple Naked Sets
14 x Pinned Squares

(Susser does not do coloring.) Anyway, basic methods get to here:
Code:
+----------------+----------------+-----------------+
| 569a 59   8    | 2    7    4    | 35   1    3569A |
| 15   125  3    | 8    9    6    | 7    4    25    |
| 7    249  469  | 1    5    3    | 69   8    269   |
+----------------+----------------+-----------------+
| 3    19   7    | 5    8    2    | 19   6    4     |
| 2    145  145  | 6    13   9    | 35   7    8     |
| 8    6    159  | 4    13   7    | 2    359  1359  |
+----------------+----------------+-----------------+
| 169C 8    1269 | 39   4    5    | 16b  239  7     |
| 4    7    259  | 39   6    1    | 8    2359 359   |
| 1569 3    1569 | 7    2    8    | 4    59   16B   |
+----------------+----------------+-----------------+

There is an XY-wing <159> in R1C2 that takes out <1> from R2C2.

There is also a fork (Turbot fish) formed by the strong links on <6> in R1 and B9. So, R7C1 is not <6>.

(Here is the reasoning: If b is <6>, C is not. If b is not <6>, B is, A is not, a is, and C is not. Either way, C is not.)

A few more basic moves get to:
Code:
+----------------+----------------+----------------+
| 56   59a  8    | 2    7    4    | 35   1    3569A|
| 1    25   3    | 8    9    6    | 7    4    25   |
| 7    249  469C | 1    5    3    | 69   8    269  |
+----------------+----------------+----------------+
| 3    19C  7    | 5    8    2    | 19   6    4    |
| 2    145  45   | 6    13   9    | 35   7    8    |
| 8    6    59b  | 4    13   7    | 2    35   19B  |
+----------------+----------------+----------------+
| 9    8    16   | 3    4    5    | 16   2    7    |
| 4    7    2    | 9    6    1    | 8    35   35   |
| 56   3    156  | 7    2    8    | 4    9    16   |
+----------------+----------------+----------------+

Now, there is a fork formed by the strong links on <9> in R1 and R6. This eliminates <9> in R3C3 and R4C2, which solves the puzzle.

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5158
Location: Rochester, NY, USA

PostPosted: Thu Aug 31, 2006 12:17 am    Post subject: Reply with quote

Quote:
There is an XY-wing <159> in R1C2 that takes out <1> from R2C2.


I also used this XY-Wing.

Quote:
There is also a fork (Turbot fish) formed by the strong links on <6> in R1 and B9. So, R7C1 is not <6>.


That is another one of my deficiencies, looking for strong links only in rows and columns, but not boxes? I never understood the Turbot fish. Is that all it is, a strong link that happens to involve a box?

Quote:
Now, there is a fork formed by the strong links on <9> in R1 and R6. This eliminates <9> in R3C3 and R4C2, which solves the puzzle.


I don't know if I ever got that far to see that strong link. As I mentioned earlier, there were a couple of finned X-Wings, which I don't recall if they were of much help, an XYZ-Wing on 359 and a second XY-Wing, this one on 235, which finished the puzzle for me.
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Thu Aug 31, 2006 1:14 am    Post subject: Reply with quote

Marty R. wrote:
I never understood the Turbot fish. Is that all it is, a strong link that happens to involve a box?


The "turbot fish" was named back in the good old days, when patterns were named by their discoverers, perhaps after a shape the pattern formed (turbot fish) or because the pattern reminded the discoverer of something else (X-wing). (Personally, I think we should talk of UR Keith instead of UR Type 6, but that ship has already sailed and docked.)

The "turbot fish' is nothing more than colouring (another name from the good, old days) but the chain always fits a certain pattern.

Code:
 
 *-----------------------------------------------------------*
 | 569   59    8     | 2     7     4     | 35    1     3569  |
 | 15    125   3     | 8     9     6     | 7     4     25    |
 | 7     249   469   | 1     5     3     | 69a   8     269   |
 |-------------------+-------------------+-------------------|
 | 3     19a   7     | 5     8     2     | 19A   6     4     |
 | 2     145   145   | 6     13    9     | 35    7     8     |
 | 8     6     159A  | 4     13    7     | 2     359   1359  |
 |-------------------+-------------------+-------------------|
 | 169   8     1269  | 39    4     5     | 16    239   7     |
 | 4     7     259   | 39    6     1     | 8     2359  359   |
 | 1569  3     1569  | 7     2     8     | 4     59    16    |
 *-----------------------------------------------------------*


This grid is from the puzzle that Keith posted but I don't think it is the 'turbot fish' that he is talking about. The 'turbot fish' always involves 4 cells. (5 if you count the cell in which the exclusion takes place.) If you were to draw solid lines that connect each strong link, plus lines from the end cells of the chain to the cell that the end cells both 'see', you would end up with a 5 sided figure, where two of the lines crossed. The configuration that the discoverer saw look liked a fish, hence the name. (Not sure where the 'turbot' came from.) The beauty of the 'turbot fish' comes from the fact that there really doesn't have to be a strong link between the 2nd & 3rd cells (r4c27 in this case) for it to work, in which case it would be multi-colouring.
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keith



Joined: 19 Sep 2005
Posts: 3165
Location: near Detroit, Michigan, USA

PostPosted: Thu Aug 31, 2006 8:19 am    Post subject: Turbot fish Reply with quote

Here is a link to the "Turbot fish" posting.

http://www.sudoku.com/forums/viewtopic.php?t=833

In one form, it looks like a fishy thingy.

As Tracy says, in a "fork", it is two strong links (two sides) that line up on one end (three sides) and at the other ends "see" a cell where an elimination can occur (five sides).

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5158
Location: Rochester, NY, USA

PostPosted: Thu Aug 31, 2006 4:54 pm    Post subject: Reply with quote

Thanks guys.

I just learned that Turbot is pronounced TUR-but, but that many Americans pronounce it TUR-boh.

Psetta maxima (Just another pretty face):

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