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immpy
Joined: 06 May 2017
Posts: 571
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 Posted: Thu Aug 27, 2020 8:52 pm Post subject: Extreme 082720 |
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One for the chain gang...
| Code: |
+-------+-------+-------+
| . . . | . 5 3 | 1 . . |
| . 1 . | 2 . . | 5 . . |
| . . . | . . 9 | . 4 7 |
+-------+-------+-------+
| . 9 . | . . 4 | 8 . 2 |
| 2 . . | . . . | . . 4 |
| 8 . 3 | 9 . . | . 5 . |
+-------+-------+-------+
| 1 6 . | 7 . . | . . . |
| . . 5 | . . 6 | . 7 . |
| . . 8 | 1 3 . | . . . |
+-------+-------+-------+
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Play this puzzle online at the Daily Sudoku site
cheers...immp |
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dongrave
Joined: 06 Mar 2014
Posts: 568
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| Posted: Fri Aug 28, 2020 12:03 pm Post subject: |
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| Code: | +-----------------+------------+----------------+
| 4679 278 24679 | 468 5 3 | 1 2689 89 |
| 3469 1 469 | 2 478 78 | 5 3689 389 |
| 356 2358 26 | 68 1 9 | 236 4 7 |
+-----------------+------------+----------------+
| 567 9 167 | 35 67 4 | 8 13 2 |
| 2 57 167 | 35 678 78 | 39 139 4 |
| 8 4 3 | 9 2 1 | 7 5 6 |
+-----------------+------------+----------------+
| 1 6 249 | 7 49 25 | 2349 2389 3589 |
| 349 23 5 | 48 489 6 | 249 7 1 |
| 479 27 8 | 1 3 25 | 2469 269 59 |
+-----------------+------------+----------------+
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This is probably the ugliest one step solution that you'll ever see but I think the logic is right. I used the symbols '*', '@', and '$' to mark cell values referenced later on in the chain. (I learned that trick recently from Clement.) The '$' is probably not needed here though because it references a cell value in the same column from just 2 steps earlier.
6r3c4-(6=2*)r3c3-(26=3@)r3c7-(3=2|4|9)r7c357-(2=5)r7c6-(5=2)r9c6-(2=7$)r9c2-(7=5)r5c2-(2*3@5=8)r3c2-(7$8=2)r1c2; contradiction (i.e. 2r3c3 and 2r1c2) => r3c4 <> 6; stte. |
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immpy
Joined: 06 May 2017
Posts: 571
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| Posted: Fri Aug 28, 2020 6:32 pm Post subject: |
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Hello Don. Now, mind you, I hate chains...despise them in fact, but I know that in some of these really tough puzzles I may have to resort to using them. So I am at least familiar with them. You may make the logic notation as ugly as you like because I say "Hats off" to you for doing it in one step! I sure am not capable of that. It took me several steps, using several wing variations, and THEN several (I recall using three) XY-Chains to solve.
cheers...immp |
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Clement
Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania
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| Posted: Sat Aug 29, 2020 7:55 pm Post subject: Extreme 082720 |
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| Code: |
+----------------------+-----------------+---------------------+
| 4679 h278 24679 | 468 5 3 | 1 c2689 89 |
| 3469 1 469 | 2 478 78 | 5 c3689 389 |
| 356 i2358 b26 |ja8-6 1 9 |b236 4 7 |
+----------------------+-----------------+---------------------+
| 567 9 167 | 35 67 4 | 8 13 2 |
| 2 57 167 | 35 678 78 | 39 139 4 |
| 8 4 3 | 9 2 1 | 7 5 6 |
+----------------------+-----------------+---------------------+
| 1 6 249 | 7 489 25 | 2349 2389 3589 |
| 349 23 5 | 48 489 6 | 249 7 1 |
|f479 g27 8 | 1 3 25 |e2469 d269 59 |
+----------------------+-----------------+---------------------+
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Oho! Same starting point and same elimination as Dongrave, may be a different route
6r3c4 - [(6=2*)r3c3 -(6)r3c7)] = r13c8 - r9c8 = (6-4)r9c7 = (4-7)r9c1 = r9c2 - (72*=8)r1c2 - r3c2 = (8)r3c4 => - 6r3c4; btte |
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