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peter urhegyi
Joined: 26 Oct 2020
Posts: 28
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 Posted: Mon Nov 09, 2020 10:47 am Post subject: First time I post a vh sudoku |
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| Code: | ..12..3..
.2...45..
4...5...2
6...4...1
..57..8..
.8...6..5
76..1...3
.......97
..23..18. |
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peter urhegyi
Joined: 26 Oct 2020
Posts: 28
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| Posted: Mon Nov 09, 2020 11:21 am Post subject: The pencilmarks grid from this 5-step VH sudoku |
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| Code: | .-------------------.--------------------.------------------.
| 589 579 1 | 2 6789 789 | 3 467 4689 |
| 389 2 36789 | 1689 36789 4 | 5 167 689 |
| 4 379 36789 | 1689 5 13789 | 679 167 2 |
:-------------------+--------------------+------------------:
| 6 379 379 | 589 4 23589 | 279 237 1 |
| 1239 1349 5 | 7 239 1239 | 8 2346 469 |
| 1239 8 3479 | 19 239 6 | 2479 2347 5 |
:-------------------+--------------------+------------------:
| 7 6 489 | 4589 1 2589 | 24 245 3 |
| 1358 1345 348 | 4568 268 258 | 246 9 7 |
| 59 459 2 | 3 679 579 | 1 8 46 |
'-------------------'--------------------'------------------' |
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immpy
Joined: 06 May 2017
Posts: 574
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| Posted: Mon Nov 09, 2020 4:28 pm Post subject: |
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Hello peter, hello all. Be forewarned, this one came up as EXTREME when I plugged it into my external program.
cheers...immp |
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immpy
Joined: 06 May 2017
Posts: 574
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| Posted: Mon Nov 09, 2020 5:12 pm Post subject: |
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Lots of neat stuff in this one peter. Even spotted a swordfish (or two). Thanks for posting.
cheers...immp |
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peter urhegyi
Joined: 26 Oct 2020
Posts: 28
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| Posted: Mon Nov 09, 2020 5:25 pm Post subject: |
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| immpy wrote: | Lots of neat stuff in this one peter. Even spotted a swordfish (or two). Thanks for posting.
cheers...immp |
Thank you. After the discovery of the 2 swordfishes thisone needs only an x-wing , an xy-wing and an xyz-wing and a few basic steps like hidden and naked doubles and or triples. |
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dongrave
Joined: 06 Mar 2014
Posts: 572
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| Posted: Mon Nov 09, 2020 6:55 pm Post subject: |
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Wow! I had a tough time with this one! After basics: | Code: |
+-----------------+-----------------+---------------+
| 589 579 1 | 2 6789 789 | 3 467 4689 |
| 389 2 36789 | 1689 36789 4 | 5 167 689 |
| 4 379 36789 | 1689 5 13 | 679 167 2 |
+-----------------+-----------------+---------------+
| 6 379 379 | 58 4 58 | 79 2 1 |
| 129 149 5 | 7 239 13 | 8 346 469 |
| 129 8 479 | 19 239 6 | 479 347 5 |
+-----------------+-----------------+---------------+
| 7 6 489 | 489 1 289 | 24 5 3 |
| 1358 1345 348 | 4568 68 258 | 246 9 7 |
| 59 459 2 | 3 679 579 | 1 8 46 |
+-----------------+-----------------+---------------+ |
4r9c9-[(4=5|9)r9c12-(59=7*)r9c6 -(4=2*)r7c7]-(24=6)r8c7-(6=8)r8c5-(2*8=9)r7c6-(7*9=8)r1c6-r3c4=r3c3-r78c3=r8c1; contradiction (i.e. 8r8c15) => r9c9 <> 4; stte. |
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dongrave
Joined: 06 Mar 2014
Posts: 572
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| Posted: Mon Nov 09, 2020 8:08 pm Post subject: |
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| Btw, the hidden pair 58 in Peter's grid is sort of hard to find if you're just looking at candidates - but while cross-hatching it's easy to notice that the 5 and 8 are in rows 5 and 6 which means they must be in r4c46 (since r4c5 is already populated). |
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storm_norm22
Joined: 24 Oct 2020
Posts: 21
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| Posted: Tue Nov 10, 2020 3:16 am Post subject: |
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almost m-wing 
you would have this m-wing
(6=4)r9c9 - (4)r9c5 = (6-4)r8c4 = (4)r7c4
which would eliminate the 4 in r7c7 if the 6 in r8c5 didn't exist.
so following the 6's along (6)r8c5 - (6)r1c5 = (6)r1c89 - (6)r3c7 = (6-2)r8c7 = (2)r7c7
put it all together
m-wing[(6=4)r9c9 - (4)r9c5 = (6-4)r8c4 = (4)r7c4] = (6)r8c5 - (6)r1c5 = (6)r1c89 - (6)r3c7 = (6-2)r8c7 = (2)r7c7; r7c7 <>4
or if you prefer, you can see it as a contradiction using the 6's in box 8
| Code: | 6r8c4 - 4r8c4 = 4r7c4
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6r8c5 - r1c5 = r1c89 - r3c7 = (6-2)r8c7 = (2)r7c7
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6r9c5 - (6=4)r9c9 |
| Code: | +-------------------+---------------------+----------------------+
| 589 579 1 | 2 789(6) 789 | 3 47(6) 489(6) |
| 389 2 36789 | 1689 36789 4 | 5 167 689 |
| 4 379 36789 | 1689 5 13 | 79(6) 167 2 |
+-------------------+---------------------+----------------------+
| 6 379 379 | 58 4 58 | 79 2 1 |
| 129 149 5 | 7 239 13 | 8 346 469 |
| 129 8 479 | 19 239 6 | 479 347 5 |
+-------------------+---------------------+----------------------+
| 7 6 489 | 89(4) 1 289 | 4(2) 5 3 |
| 1358 1345 348 | 58(46) 8(6) 258 | 4(26) 9 7 |
| 59 459 2 | 3 79(6) 579 | 1 8 (46) |
+-------------------+---------------------+----------------------+ |
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immpy
Joined: 06 May 2017
Posts: 574
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| Posted: Tue Nov 10, 2020 4:30 pm Post subject: |
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Yes norm, used something related, believed it was an actual M-Wing, but I came to it via a different path. So many options and good rinsing/scanning skills needed in this one. Thanks again peter.
cheers...immp |
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storm_norm22
Joined: 24 Oct 2020
Posts: 21
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| Posted: Tue Nov 10, 2020 4:57 pm Post subject: |
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| immpy wrote: | Yes norm, used something related, believed it was an actual M-Wing, but I came to it via a different path. So many options and good rinsing/scanning skills needed in this one. Thanks again peter.
cheers...immp |
agreed, nice puzzle from peter |
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