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immpy
Joined: 06 May 2017
Posts: 571
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 Posted: Wed Dec 20, 2017 1:33 pm Post subject: Extra Hard 122017 |
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Enjoy the puzzle...Merry Christmas!
| Code: |
+-------+-------+-------+
| . . . | . . . | . . . |
| . 4 2 | 7 . 9 | 5 8 . |
| 5 1 . | . . . | . 7 9 |
+-------+-------+-------+
| . . 1 | 8 . 4 | 9 . . |
| . 2 . | . . . | . 3 . |
| . . 3 | 2 . 6 | 7 . . |
+-------+-------+-------+
| 2 6 . | . . . | . 9 5 |
| . 8 7 | 4 . 5 | 6 2 . |
| . . . | . . . | . . . |
+-------+-------+-------+
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Play this puzzle online at the Daily Sudoku site |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Thu Dec 21, 2017 4:13 am Post subject: |
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here is after basics
| Code: | ┌──────────────────────────┬──────────────────────────┬──────────────────────────┐
│ 36789 379 689 │ 1356 124568 1238 │ 1234 146 1346 │
│ │ │ │
│ 36 4 2 │ 7 16 9 │ 5 8 136 │
│ │ │ │
│ 5 1 68 │ 36 2468 238 │ 234 7 9 │
├──────────────────────────┼──────────────────────────┼──────────────────────────┤
│ 67 57 1 │ 8 3 4 │ 9 56 2 │
│ │ │ │
│ 4689 2 5689 │ 159 1579 17 │ 14 3 1468 │
│ │ │ │
│ 489 59 3 │ 2 159 6 │ 7 145 148 │
├──────────────────────────┼──────────────────────────┼──────────────────────────┤
│ 2 6 4 │ 13 178 1378 │ 138 9 5 │
│ │ │ │
│ 139 8 7 │ 4 19 5 │ 6 2 13 │
│ │ │ │
│ 139 359 59 │ 1369 12689 1238 │ 1348 14 7 │
└──────────────────────────┴──────────────────────────┴──────────────────────────┘ |
XY-Wing (36-1) pivot r3c4=> -1r1c4,r789c5
Here is after the XY-Wing
| Code: | +---------------+----------------+---------------+
| 36789 379 689 | 5 12468 1238 | 1234 146 1346 |
| 36 4 2 | 7 16 9 | 5 8 136 |
| 5 1 68 | 36 2468 238 | 234 7 9 |
+---------------+----------------+---------------+
| 67 57 1 | 8 3 4 | 9 56 2 |
| 468 2 568 | 9 157 17 | 14 3 1468 |
| 489 59 3 | 2 15 6 | 7 145 148 |
+---------------+----------------+---------------+
| 2 6 4 | 13 78 378 | 138 9 5 |
| 13 8 7 | 4 9 5 | 6 2 13 |
| 139 359 59 | 136 268 238 | 1348 14 7 |
+---------------+----------------+---------------+ |
XY-Chain (9=5)r6c2- (5=76)r4c21-(6=319)r289c1=> -9r9c2,r6c1
here is after the XY-Chain
| Code: | +--------------+----------------+---------------+
| 36789 37 689 | 5 12468 1238 | 1234 146 1346 |
| 36 4 2 | 7 16 9 | 5 8 136 |
| 5 1 68 | 36 2468 238 | 234 7 9 |
+--------------+----------------+---------------+
| 67 57 1 | 8 3 4 | 9 56 2 |
| 468 2 568 | 9 157 17 | 14 3 1468 |
| 48 9 3 | 2 15 6 | 7 145 148 |
+--------------+----------------+---------------+
| 2 6 4 | 13 78 378 | 138 9 5 |
| 13 8 7 | 4 9 5 | 6 2 13 |
| 139 35 59 | 136 268 238 | 1348 14 7 |
+--------------+----------------+---------------+
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One more wing finishes it.
XY-Wing (36-7) pivot r2c1=> -7r1c1,r4c2 |
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immpy
Joined: 06 May 2017
Posts: 571
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| Posted: Fri Dec 22, 2017 12:32 pm Post subject: |
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Very nice Marty.
You are very good (it seems) with chains; I, unfortunately, am not. I get stupefied just trying to follow your path, and end up staring blankly at the puzzle, none the wiser. Consequently, this puzzle took me a bit longer to solve. I used the same initial XY- Wing (36-1), rinsed, found an X-Wing on 3 in r28 c19 which helped marginally, then basically resorted to looking for contradictions via the "if this is true...then that becomes" procedure. It always pays to keep a nice eraser handy...lol.
I eventually solved it, but your approach was by far quicker, and cleaner, as well.
Thanks, Marty, for posting it. |
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