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March 18 VH
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Victor



Joined: 29 Sep 2005
Posts: 207
Location: NI

PostPosted: Thu Mar 20, 2008 10:49 am    Post subject: Reply with quote

Craig wrote:
Quote:
the creators should have stopped at Type 5

I do agree that this kind of UR is weird. But I don't see that you can ban this kind without banning them all (which I believe some people do, which is fair enough).
[I like URs in general because (a) they sometimes solve puzzles that other methods don't seem to touch and (b) they can produce neat logic. I jokingly suggested a style judge once. No prizes for this VH, which produced nothing really interesting. But in the previous one Marty was the definite winner (having screwed up 1st time round!) - an elegant little bit of logic that depended on UR thinking. No UR = no nice logic here.]
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ravel



Joined: 21 Apr 2006
Posts: 536

PostPosted: Thu Mar 20, 2008 6:51 pm    Post subject: Reply with quote

Earl wrote:
The HINT on Draw/Play says that the next move in this grid is 8 in R2C5.

Why?
Code:
+------------+-----------+------------+
| 5 48  469  | 1  7  246 | 269 68 3   |
| 3 1   69   | 26 89 5   | 4   7  268 |
| 2 478 4679 | 3  89 46  | 569 1  568 |
+------------+-----------+------------+
| 9 3   1    | 4  26 8   | 57  26 57  |
| 7 6   2    | 5  1  3   | 8   9  4   |
| 8 45  45   | 9  26 7   | 1   3  26  |
+------------+-----------+------------+
| 1 2   37   | 68 5  9   | 367 4  678 |
| 4 9   8    | 7  3  26  | 26  5  1   |
| 6 57  357  | 28 4  1   | 37  28 9   |
+------------+-----------+------------+

I suppose the program did, what most here did - x-wing [Edit typo:] r1c8<>2 (already done in this grid), xy-wing r13c7<>6, locked candidate box 9 r7c9<>6, xyz-wing r3c9<>6, triple 578 in column 9 r2c9<>8. So the next number after this long way is r2c5=8.
Btw. i missed something and solved it with a chain similar to George's one ...


cgordon wrote:

Code:
               
+-------+-------+------+   
| . . 7 | . . . | 3 . .|   
| . . . | . . . | . . .|   
| . . 3 | . . . | 7 . .|
+-------+-------+------+


What's Deadly about that?? There aren't two options (I don't think)
.
I can understand your doubts. Nataraj already explained it, but maybe it helps to say it in other words again, because it needs a bit theory understanding.

Suppose you have such a pattern, it leads to a solution and (important) none of the 4 numbers was a given. Then in this solution there cannot be a 3 or 7 in the same rows, columns or boxes. So you can xx the 2 numbers (none was given) and you get a second solution.

So any assumption that leads to this pattern must be false, in the example case the assumption that the x-wing number is in the 3 value-cell.


Last edited by ravel on Sat Mar 22, 2008 9:15 am; edited 1 time in total
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Thu Mar 20, 2008 8:27 pm    Post subject: Reply with quote

Quote:
tsk tsk, I am away for a day, and look what happens!


Keith,
being gone for a day warrants a tsk tsk??

so you get a tsk tsk for being gone for a day.

what kind reaction do you have for the amount of time since samgj has posted in the "daily sudoku puzzle" thread?

I guess I am curious as to the lay off?
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nataraj



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

PostPosted: Thu Mar 20, 2008 8:58 pm    Post subject: Reply with quote

storm_norm wrote:
what kind reaction do you have for the amount of time since samgj has posted in the "daily sudoku puzzle" thread?


Hm. That would be 242*2=484 "tsk"s. Easy question.
Laughing Laughing Laughing
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crunched



Joined: 05 Feb 2008
Posts: 168

PostPosted: Sat Mar 22, 2008 3:04 am    Post subject: Reply with quote

Please excuse my simpleton level, but I do not understand where there is an x-wing on 2. Could somebody please point that out?
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ravel



Joined: 21 Apr 2006
Posts: 536

PostPosted: Sat Mar 22, 2008 9:12 am    Post subject: Reply with quote

Sorry, this was my fault. I had copied Earl's grid, where the 2 in r1c8 already was eliminated. This was the x-wing i had in mind. Of course you cannot eliminate 2 in r1c7. Here is Victors grid:
Code:
+------------+-----------+-------------+
| 5 48  469  | 1  7 *246 |*269 268 3   |
| 3 1   69   | 26 89 5   | 4   7   268 |
| 2 478 4679 | 3  89 46  | 569 1   568 |
+------------+-----------+-------------+
| 9 3   1    | 4  26 8   | 57  26  57  |
| 7 6   2    | 5  1  3   | 8   9   4   |
| 8 45  45   | 9  26 7   | 1   3   26  |
+------------+-----------+-------------+
| 1 2   37   | 68 5  9   | 367 4   678 |
| 4 9   8    | 7  3 *26  |*26  5   1   |
| 6 57  357  | 28 4  1   | 37  28  9   |
+------------+-----------+-------------+
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