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Super Hard 062718

 
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immpy



Joined: 06 May 2017
Posts: 570

PostPosted: Wed Jun 27, 2018 9:17 pm    Post subject: Super Hard 062718 Reply with quote

This one took me quite a while to solve, and indeed almost stumped me.
Maybe the 1-step solvers can crack it more rapidly. I post it because it is simply one of THE hardest puzzles I ever completed. Enjoy all...

Code:

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

Play this puzzle online at the Daily Sudoku site

cheers...immp
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ZeroAssoluto



Joined: 05 Feb 2017
Posts: 868
Location: Rimini, Italy

PostPosted: Wed Jun 27, 2018 11:03 pm    Post subject: Reply with quote

Hi everyone,

Code:

+--------------+--------+--------------+
| 246  49  5   | 7 8  1 | 3   269 269  |
| 1    78  28  | 6 3  9 | 27  4   5    |
| 367  379 39  | 2 5  4 | 679 8   1    |
+--------------+--------+--------------+
| 348  1   348 | 9 6  5 | 248 7   248  |
| 78   789 6   | 4 1  2 | 5   3   89   |
| 5    2   49  | 3 7  8 | 469 1   469  |
+--------------+--------+--------------+
| 24   5   1   | 8 9  3 | 246 26  7    |
| 9    6   248 | 1 24 7 | 248 5   3    |
| 2348 348 7   | 5 24 6 | 1   29  2489 |
+--------------+--------+--------------+

Play this puzzle online at the Daily Sudoku site

Discontinuos Nice Loop (?) from r1c2;
if r1c2=9 r3c3=3 r9c2=3 and no number 4 in c2;
so r1c2=4 and basic.

Ciao Gianni
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immpy



Joined: 06 May 2017
Posts: 570

PostPosted: Thu Jun 28, 2018 1:38 am    Post subject: Reply with quote

Elegant solution Gianni. Beautiful. I was unable to spot the Discontinuous Nice Loop. I was forced to resort to a finned XY-Wing at this stage, on the 248.
The pivot is located at r8c3 and contains the fin (extra candidate) 2. The pincers are located at r2c3 (28) and r7c1 (24).

In this instance the fin proved true with r8c3=2! I know there are some in the community who frown on this approach, equating it with guessing, but when I have nothing else to grasp onto, as was my dilemma here, I will use it gladly.

As a refresher....EITHER the fin (in this case 2) is true; OR the XY-Wing
(-248) is true. The eliminations that would be made via the XY-Wing eventually lead to a contradiction, thus it is false.

cheers all...immp
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