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A.Sudoku 4/08/2018

 
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AjÚ Dimonios



Joined: 01 May 2017
Posts: 325
Location: Sassari Italy

PostPosted: Sun Aug 05, 2018 7:13 am    Post subject: A.Sudoku 4/08/2018 Reply with quote

Hy everyone
How many moves after the basic strategy?
Code:

+-------+-------+-------+
| . . . | 4 9 3 | . . . |
| . . 9 | 1 . 2 | 6 . . |
| 7 . . | . . . | . . 4 |
+-------+-------+-------+
| . 5 . | . 3 . | . 6 . |
| . . . | 5 . 1 | . . . |
| . 3 . | . 8 . | . 2 . |
+-------+-------+-------+
| 8 . . | . . . | . . 1 |
| . . 7 | 9 . 6 | 8 . . |
| . . . | 8 4 5 | . . . |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site
Ciao a Tutti
Paolo
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dongrave



Joined: 06 Mar 2014
Posts: 326

PostPosted: Sun Aug 05, 2018 5:35 pm    Post subject: Reply with quote

Sorry, this one's too tough for me! Here's the grid after basics I think.
Code:
+----------------+------------+----------------+
| 1256 1268 1256 | 4   9   3  | 257  1578 2578 |
| 345  48   9    | 1   7   2  | 6    358  358  |
| 7    12   123  | 6   5   8  | 239  139  4    |
+----------------+------------+----------------+
| 149  5    148  | 2   3   49 | 147  6    789  |
| 249  7    248  | 5   6   1  | 34   348  389  |
| 1469 3    146  | 7   8   49 | 145  2    59   |
+----------------+------------+----------------+
| 8    469  456  | 3   2   7  | 459  459  1    |
| 2345 24   7    | 9   1   6  | 8    345  235  |
| 123  129  123  | 8   4   5  | 2379 379  6    |
+----------------+------------+----------------+

I think I counted 7 different cells that if you have the right number you can solve it in one step but unfortunately I couldn't find any way to reach a contradiction when assuming that the cell did not contain the right value without using advanced moves (even if you assume each of the wrong values one at a time). Where did you find this one? This one is brutal!
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immpy



Joined: 06 May 2017
Posts: 199

PostPosted: Sun Aug 05, 2018 10:53 pm    Post subject: Reply with quote

This is TOO TOUGH....for me, anyway. I can't budge it. I pasted it into my solver, and it came up with numerous grouped discontinuous nice loops and several Kraken Fishes (actually Finned Franken Jellyfishes), and several Almost Locked Sets, among other things more familiar. I remain stumped and look forward to more manageable puzzles. I counted 17 advanced steps that my program needed to solve. Which is why I avoided this one when you first posted it back in April.

cheers...immp
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AjÚ Dimonios



Joined: 01 May 2017
Posts: 325
Location: Sassari Italy

PostPosted: Mon Aug 06, 2018 6:59 am    Post subject: Reply with quote

Hy everyone.
Dongrave wrote:
Code:
I think I counted 7 different cells that if you have the right number you can solve it in one step but unfortunately I couldn't find any way to reach a contradiction when assuming that the cell did not contain the right value without using advanced moves (even if you assume each of the wrong values one at a time). Where did you find this one? This one is brutal!

It is true there are 7 Backdoors im this puzzle.
It is resolved in two moves with the technique of the slopes. It is sufficient to show that R9C2 ≠ 9. In fact R9C2 = 9 + R8C2 = 2 and R9C2 = 9 + R8C2 = 4 create, using only the basic technique, both of the contradictions and consequently make the cell R8C2 empty when R9C2 is equal to 9. For this reason R9C2 is different from 9.

Ciao a Tutti Paolo
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dongrave



Joined: 06 Mar 2014
Posts: 326

PostPosted: Mon Aug 06, 2018 8:06 pm    Post subject: Reply with quote

Oh, of course! Very interesting! I didn't think of that! Thanks!
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