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01-04-2023-vh+

 
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peter urhegyi



Joined: 26 Oct 2020
Posts: 28
PostPosted: Sat Apr 01, 2023 9:53 am    Post subject: 01-04-2023-vh+ Reply with quote
Code:

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

Play this puzzle online at the Daily Sudoku site
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dongrave



Joined: 06 Mar 2014
Posts: 564
PostPosted: Sat Apr 01, 2023 8:48 pm    Post subject: Reply with quote
Wow! This was a tough one! You know how many cells I solved using basics? None!

I couldn't find a single step solution so I used 2 steps.

After basics:
Code:
+------------------------+--------------------+--------------------+
|  9       3678    34568 | 3458  2     134568 | 1357   1358  1378  |
|  34578   1       3458  | 34589 389   3458   | 2357   6     23789 |
|  358     368     2     | 7     13689 13568  | 135    13589 4     |
+------------------------+--------------------+--------------------+
|  23478   23678   1     | 2358  378   23578  | 9      348   2368  |
|  2378    236789  3689  | 2389  4     12378  | 1236   138   5     |
|  2348    5       3489  | 6     1389  1238   | 1234   7     1238  |
+------------------------+--------------------+--------------------+
| d123     4      b39    | 23    5     67     | 8     c139   67    |
|  1358    38      7     | 348   368   9      | 13456  2     136   |
|  6     ae2389    3589  | 1     378   23478  | 3457   3459  379   |
+------------------------+--------------------+--------------------+

Step 1: 9r9c2-r7c3=(9-1)r7c8=(1-2)r7c1=r9c2 contradiction (i.e. 9r9c2, 2r9c2).

Code:
+-----------------+--------------+-------------+
|  9     7    6   |  345 2   345 | 1   58  38  |
|  345   1    345 |  9   38  358 | 2   6   7   |
|  358   38   2   |  7   1   6   | 35  9   4   |
+-----------------+--------------+-------------+
|  2348  6    1   | c358 7  c358 | 9  d48  238 |
|  7     9   a38* | b38  4   2   | 6   1   5   |
|  2348  5    348 |  6   9   1   | 34  7   238 |
+-----------------+--------------+-------------+
|  1     4    9   |  2   5   7   | 8   3   6   |
| g358  g38   7   | h348 6   9   | 45  2   1   |
|  6     2   f358 |  1   38  348 | 7  e45  9   |
+-----------------+--------------+-------------+

Step 2: 8*r5c3-(8=3)r5c4-(3=5|8)r4c46-(8=4)r4c8-(4=5)r9c8-(58*=3)r9c3-r8c12=r8c4 contradiction (i.e. 3r58c4) => r5c3 <> 8; stte.
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glesco



Joined: 12 May 2022
Posts: 35
PostPosted: Sun Apr 02, 2023 8:13 pm    Post subject: Reply with quote
Excellent puzzle! Didn't solve; going to try again.

Please post more if you have any!
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immpy



Joined: 06 May 2017
Posts: 570
PostPosted: Tue Apr 04, 2023 9:47 pm    Post subject: Reply with quote
Ahhh. The rarely identified and and even more rarely used (by me) Swordfish pattern. It is in there; albeit near impossible to locate. And that is only my first step.

Swordfish: (9) r367 c358 => r2c5,r59c3,r9c8<>9.
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immpy



Joined: 06 May 2017
Posts: 570
PostPosted: Tue Apr 04, 2023 9:57 pm    Post subject: Reply with quote
This reveals a Naked Triple in c5 of (378). Followed by many singles (hidden and naked), Locked candidates (pointing), and a Naked and Hidden Pair. Then some more singles.
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immpy



Joined: 06 May 2017
Posts: 570
PostPosted: Tue Apr 04, 2023 10:10 pm    Post subject: Reply with quote
That brings me here:

Code:

+-------------+------------+-----------+
| 9    7  6   | 345 2  345 | 1  58 38  |
| 345  1  345 | 9   38 358 | 2  6  7   |
| 358  38 2   | 7   1  6   | 35 9  4   |
+-------------+------------+-----------+
| 2348 6  1   | 358 7  358 | 9  48 238 |
| 7    9  38  | 38  4  2   | 6  1  5   |
| 2348 5  348 | 6   9  1   | 34 7  238 |
+-------------+------------+-----------+
| 1    4  9   | 2   5  7   | 8  3  6   |
| 358  38 7   | 348 6  9   | 45 2  1   |
| 6    2  358 | 1   38 348 | 7  45 9   |
+-------------+------------+-----------+

Play this puzzle online at the Daily Sudoku site
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immpy



Joined: 06 May 2017
Posts: 570
PostPosted: Tue Apr 04, 2023 10:12 pm    Post subject: Reply with quote
Used an X-Wing: (5) r38 c17 => r2c1<>5.
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immpy



Joined: 06 May 2017
Posts: 570
PostPosted: Tue Apr 04, 2023 10:17 pm    Post subject: Reply with quote
Now an Empty Rectangle: (3) in b7 (r5c34) => r8c4<>3. Followed by Locked candidates (3) pointing in box 8.
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immpy



Joined: 06 May 2017
Posts: 570
PostPosted: Tue Apr 04, 2023 10:20 pm    Post subject: Reply with quote
And my last Empty Rectangle: (8) in b7 (r5c34) => r8c4<>8. stte
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immpy



Joined: 06 May 2017
Posts: 570
PostPosted: Tue Apr 04, 2023 10:23 pm    Post subject: Reply with quote
Whew! That was indeed a very tough puzzle. Thank you Peter for submitting it.

cheers...immp
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