Need clarification!!

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Need clarification!!

Postby Kent » Sat Mar 18, 2006 6:10 am

Can I exclude 6 from the cell of r1c4 since it is in the same box as the fin(the cell marked with 3) which is using finned x-wing?? Need to confirm whether my understanding is right or not.


Code: Select all
+-------------------+-------------------+-------------------+
| 7     34    2     | -346   5     1    | 8     46    9     |
| 1     3459  8     | *346  #267   2479 | 2457  24567 *256  |
| 6     459   49    | 8     27    2479  | 2457  1     3     |
+-------------------+-------------------+-------------------+
| 2     1     7     | 5     9     3     | 6     8     4     |
| 9     8     3     | 7     4     6     | 25    25    1     |
| 4     6     5     | 2     1     8     | 3     9     7     |
+-------------------+-------------------+-------------------+
| 3     2     1     | 9     67    5     | 47    467   8     |
| 5     479   49    | *46   8    247    | 1     3     *26   |
| 8     47    6     | 1     3    247    | 9     2457  25    |
+-------------------+-------------------+-------------------+
Last edited by Kent on Sat Mar 18, 2006 11:39 am, edited 1 time in total.
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Postby vidarino » Sat Mar 18, 2006 9:47 am

Unfortunately not. There is a 6 in R2C8 which prevents this from forming a clean X-Wing. (It could be regarded as an extra fin, but since it cannot "see" the target cell, no elimination can be done.)
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Postby Kent » Sat Mar 18, 2006 10:42 am

Can the r2c8 also be a fin?? So there are 2 fins.One that can eliminate the 6 with minus sign and one that can't eliminate anything,
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Postby vidarino » Sat Mar 18, 2006 11:24 am

Kent wrote:Can the r2c8 also be a fin?? So there are 2 fins.One that can eliminate the 6 with minus sign and one that can't eliminate anything,


No, because we only know that
a) neither of the fins are true, in which case we end up with a regular X-Wing that can do the elimination...
or
b) one of the fins are true. In this case, since there aren't any cells that can see both the fins, we can't do an elimination.

If both fins had been in the same box, we might be able to eliminate it after all, since the target would see both fins. Because;
a) if neither fin is true, it would be zapped by the X-Wing.
or
b) it would be zapped by the fin, since they share box.
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Postby Kent » Sat Mar 18, 2006 3:41 pm

So how would i continue fr there?
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Postby Neunmalneun » Sat Mar 18, 2006 4:49 pm

I think R1C4 can be the fin with elimination the 6 from R2C5.
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Postby Hud » Sat Mar 18, 2006 4:49 pm

One elimination would be to remove the 2 from c6 in box 2 due to locked 2 in col 5 box2.
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Postby Kent » Sat Mar 18, 2006 4:56 pm

Neu
I think R1C4 can be the fin with elimination the 6 from R2C5.


Yeah.Didn't see that.Should exchange minus sign with # sign.thanks
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Postby PhilC » Sat Mar 18, 2006 8:50 pm

You could also do a sashimi x-wing in r18c49.

Code: Select all
+-------------------+-------------------+-------------------+
| 7     34    2     | *346   5     1    | 8    #46   *9     |
| 1     3459  8     |  346   267   2479 | 2457  24567 -256  |
| 6     459   49    | 8     27    2479  | 2457  1     3     |
+-------------------+-------------------+-------------------+
| 2     1     7     | 5     9     3     | 6     8     4     |
| 9     8     3     | 7     4     6     | 25    25    1     |
| 4     6     5     | 2     1     8     | 3     9     7     |
+-------------------+-------------------+-------------------+
| 3     2     1     | 9     67    5     | 47    467   8     |
| 5     479   49    | *46   8    247    | 1     3     *26   |
| 8     47    6     | 1     3    247    | 9     2457  25    |
+-------------------+-------------------+-------------------+
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Postby ronk » Sat Mar 18, 2006 10:21 pm

PhilC wrote:You could also do a sashimi x-wing in r18c49.

That's just a simple old turbot fish.

Ron
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Postby QBasicMac » Sat Mar 18, 2006 10:37 pm

I get this far

Code: Select all
+---------+----------+-------------+
| 7  3  2 | 6  5   1 | 8    4   9  |
| 1  9  8 | 3  27  4 | 257  6   25 |
| 6  5  4 | 8  27  9 | 27   1   3  |
+---------+----------+-------------+
| 2  1  7 | 5  9   3 | 6    8   4  |
| 9  8  3 | 7  4   6 | 25   25  1  |
| 4  6  5 | 2  1   8 | 3    9   7  |
+---------+----------+-------------+
| 3  2  1 | 9  6   5 | 4    7   8  |
| 5  7  9 | 4  8   2 | 1    3   6  |
| 8  4  6 | 1  3   7 | 9    25  25 |
+---------+----------+-------------+

and, using T&E, find that r2c5=2 leads to a solution. But so does r2c5=7. In fact it leads to two solutions.

So something must be wrong here.

Mac
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Postby tso » Sat Mar 18, 2006 11:39 pm

Here's an odd coincident -- don't know if it means anything. The puzzle does indeed have three solutions. If you didn't know this, looking at the candidate grid that QBasicMac posted it *looks* like a BUG situation in which r2c7 would be 2. In reality, each of the three candidates in r2c7 leads to one of the three solutions.

Now, yesterday, for no good reason, I was trying to create some Sudokus with multiple solutions, preferable 2 or 3. I found this one below with three solutions. (Unfortunately, 66 of the cells are the same in all three solutions -- it would be a better puzzle if that number was lower.)

Code: Select all
 . . . | . . 1 | 9 . .
 . 9 . | . . 7 | . 3 8
 2 . . | 3 . 6 | . . .
-------+-------+------
 . . . | 2 . . | 4 . .
 . . 4 | . . . | 6 . .
 . . 5 | . . 3 | . . .
-------+-------+------
 . . . | 5 . 8 | . . 1
 4 5 . | 9 . . | . 7 .
 . . 8 | 7 . . | . . .


These 66 numbers are the same in all three solutions (It would be a better puzzle if that number was much lower.)

Code: Select all
 5 4 3 | 8 2 1 | 9 6 7
 1 9 6 | 4 5 7 | 2 3 8
 2 8 7 | 3 9 6 | 1 5 4
-------+-------+------
 . . 9 | 2 . 5 | 4 . 3
 . . 4 | 1 . 9 | 6 . 5
 8 . 5 | 6 4 3 | 7 . .
-------+-------+------
 9 7 2 | 5 6 8 | 3 4 1
 4 5 1 | 9 3 2 | 8 7 6
 . . 8 | 7 1 4 | 5 . .



Code: Select all
 *--------------------------------------------------*
 | 5    4    3    | 8    2    1    | 9    6    7    |
 | 1    9    6    | 4    5    7    | 2    3    8    |
 | 2    8    7    | 3    9    6    | 1    5    4    |
 |----------------+----------------+----------------|
 | 67   16   9    | 2    78   5    | 4    18   3    |
 | 37   23   4    | 1    78   9    | 6    28   5    |
 | 8    12   5    | 6    4    3    | 7    129  29   |
 |----------------+----------------+----------------|
 | 9    7    2    | 5    6    8    | 3    4    1    |
 | 4    5    1    | 9    3    2    | 8    7    6    |
 | 36   36   8    | 7    1    4    | 5    29   29   |
 *--------------------------------------------------*


Lo -- just as in the posted puzzle, it *looks* like simple BUG in which r6c8 must be 2. Of course since the puzzle has more than one solution, BUG (and UR) cannot be used. Each of the three candidates in r6c8 lead to one of the three answers.
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