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Vanhegan

 
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Marty R.



Joined: 12 Feb 2006
Posts: 5175
Location: Rochester, NY, USA

PostPosted: Sat Jul 20, 2013 1:28 am    Post subject: Vanhegan Reply with quote

Code:

+------------------+-------------+---------------+
| 4     68    2    | 358 1   9   | 367 3567 358  |
| 5     189   7    | 38  6   4   | 2   139  1389 |
| 13689 1689  1369 | 7   2   58  | 4   1569 1589 |
+------------------+-------------+---------------+
| 7     3     59   | 25  89  6   | 1   459  459  |
| 1269  12569 4    | 15  39  7   | 8   3569 359  |
| 1689  15689 1569 | 4   389 15  | 36  2    7    |
+------------------+-------------+---------------+
| 1369  14679 8    | 19  5   2   | 37  1347 134  |
| 1239  1279  139  | 189 4   138 | 5   1378 6    |
| 13    145   135  | 6   7   138 | 9   1348 2    |
+------------------+-------------+---------------+

Play this puzzle online at the Daily Sudoku site

I've reached an invalidity twice and I wonder if I've erred in logic rather than the usual mechanical errors.

First move is a Fin Transport which I think is OK. Based on the 6s in r57 I think 6 can be eliminated from r1c2 after transporting 6 from r5c8 to r1c7.

I'm less confident about this move. Note the DP on 12 in r58c12. The 2 is an X-Wing. I treated each line as a Type 4 and removed 1 from all four cells. Is this where I went wrong?
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keith



Joined: 19 Sep 2005
Posts: 3182
Location: near Detroit, Michigan, USA

PostPosted: Sat Jul 20, 2013 7:34 am    Post subject: Reply with quote

Marty,

I think your DP X-wing reasoning is faulty.

Look at it this way: One of the two diagonals must be 2. Pick one.

If one of the remaining cells is 1, does it force 1 in the fourth cell of the X-wing? I think not, and eliminations of 1 in the DP cannot be made.

I believe Helmut's Sudoku Helper will tell you this is a valid puzzle. I presume it will also show that the solution includes 1 on one of the corners of the X-wing.

From a hotel in the suburbs of Toronto.

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5175
Location: Rochester, NY, USA

PostPosted: Sat Jul 20, 2013 2:55 pm    Post subject: Reply with quote

Quote:
If one of the remaining cells is 1, does it force 1 in the fourth cell of the X-wing? I think not, and eliminations of 1 in the DP cannot be made.


Keith,

Thanks. What I did, cell by cell, was place 1 in the cell and saw that it led to a DP. I was looking at the trees, not the forest.

Marty
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