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Unfair 040420

 
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immpy



Joined: 06 May 2017
Posts: 297

PostPosted: Sun Apr 05, 2020 12:16 am    Post subject: Unfair 040420 Reply with quote

Hello everyone,
Enjoy the puzzle...

Code:

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

Play this puzzle online at the Daily Sudoku site

cheers...immp
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Clement



Joined: 24 Apr 2006
Posts: 1018
Location: Dar es Salaam Tanzania

PostPosted: Tue Apr 07, 2020 9:22 am    Post subject: Unfair 040420 Reply with quote

Three Steps
Code:

+-------------------------+-------------------+------------------------+
| 2        7         456  | 456     9     8   | 1        34       345  |
| 456      9         1456 | 3       7     156 | 2        48       458  |
| 458      3         1458 | 45      2     15  |{79}      79       6    |
+-------------------------+-------------------+------------------------+
| 3        1         68   | 2       5     9   | 468      468      7    |
| 7        68        2    | 1       3     4   | 5        68       9    |
| 9        45        45   | 67      8     67  | 3        1        2    |
+-------------------------+-------------------+------------------------+
| 1        2458      7    | 58      6     25  |{489}     239-48   3-48 |
| 4568     24568     9    | 578     1     3   |{4678}    27-468  {48}  |
| 68       268       3    | 9       4     27  |{678}     5        1    |
+-------------------------+-------------------+------------------------+

Step 1: Sue-De-Coq AALS in Box 9 {46789}r789c7.Other Cells {48}r8c9 in the Box and {79}r3c7 along the column.
Eliminations: Candidates which can see ALL the candidates inside the pattern => - 48r7c89,468r8c8(does not solve it) Unfair
Code:

+-------------------------+--------------------+----------------------+
| 2        7         456  |b456      9     8   | 1        3       45  |
| 456      9         1456 | 3        7    a156 | 2        48      458 |
| 458      3         1458 |b45       2    a15  | 79       79      6   |
+-------------------------+--------------------+----------------------+
| 3        1         68   | 2       5      9   | 468      468     7   |
| 7        68        2    | 1       3      4   | 5        68      9   |
| 9        45        45   | 67      8      67  | 3        1       2   |
+-------------------------+--------------------+----------------------+
| 1        2458      7    |b58      6     a25  | 489      9-2     3   |
| 4568     24568     9    |b578     1      3   | 4678    c27      48  |
| 68       268       3    | 9       4      27  | 678      5       1   |
+-------------------------+--------------------+----------------------+

Step 2: (2=516)r732c6 - (6=4587)r1378c4 = (7=2)r8c8 => - 2r7c8
Code:

+-----------------------+--------------------+--------------------+
| 2       7       f456  |g456      9     8   | 1      3       45  |
| 456     9        1456 | 3        7     156 | 2      48      458 |
| 458     3        1458 | 45       2     15  | 9      7       6   |
+-----------------------+--------------------+--------------------+
| 3       1       e68   | 2        5     9   |e48     468     7   |
| 7       68       2    | 1        3     4   | 5      68      9   |
| 9       45       45   |h67       8    i67  | 3      1       2   |
+-----------------------+--------------------+--------------------+
| 1      c245      7    | 58       6     25  |d48      9      3   |
| 456     456      9    | 578      1     3   | 67      2      48  |
| 68     b268      3    | 9         4   ja7-2| 67      5      1   |
+-----------------------+--------------------+--------------------+

Step 3: (2)r9c6 - r9c2 = (2-4)r7c2 = r7c7 - (4=86)r4c73 - (6)r1c3 = r1c4 - (6=7)r6c4 - r6c6 = (7)r9c6 => - 2r9c6; stte
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immpy



Joined: 06 May 2017
Posts: 297

PostPosted: Tue Apr 07, 2020 4:11 pm    Post subject: Reply with quote

Yesss!! A beautiful use of the Sue de Coq, and I unfortunately missed it. I am thinking that because the 6 also got "locked" into the pattern, that any 6 in r7 and box9 (outside of the intersecting cells) could also have been eliminated. Not sure if this would have solved much further. I may bring this puzzle up again in my program to test this out. I absolutely LOVE the Sue de Coq and I don't like missing them. Superbly executed Clement.

cheers...immp
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immpy



Joined: 06 May 2017
Posts: 297

PostPosted: Tue Apr 07, 2020 4:33 pm    Post subject: Reply with quote

Hello all,
I see now why I missed the Sue de Coq. It was no longer available due to the Naked Triple (468) in r245c8, which essentially made the same eliminations. Still a nice technique. I needed something similar to Clement's last two steps to solve as well.

cheers...immp
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Clement



Joined: 24 Apr 2006
Posts: 1018
Location: Dar es Salaam Tanzania

PostPosted: Tue Apr 07, 2020 7:47 pm    Post subject: Reply with quote

immpy wrote:
Hello all,
I see now why I missed the Sue de Coq. It was no longer available due to the Naked Triple (468) in r245c8, which essentially made the same eliminations. Still a nice technique. I needed something similar to Clement's last two steps to solve as well.

cheers...immp
Your quite right "immmpy". Shame upon on me! I couldn't see the naked triple.
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