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George Woods
Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK
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 Posted: Mon Aug 20, 2007 2:23 pm Post subject: What is this called |
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The following puzzle came from the telegraph and was graded as too Hard
This is the state after standard moves
| Code: |
+-------+-------+-------+
| 5 1 . | 3 2 . | 4 9 . |
| . . . | . 5 4 | . 1 3 |
| 3 . 4 | 6 1 9 | 5 . 2 |
+-------+-------+-------+
| 8 . 5 | 2 . . | 1 . 9 |
| . 6 . | 1 9 5 | . 4 . |
| 9 . 1 | . . . | 2 . 5 |
+-------+-------+-------+
| 1 . . | 5 7 . | . . 4 |
| 4 5 . | 9 8 . | . . 1 |
| . 2 . | 4 . 1 | . 5 . |
+-------+-------+-------+
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Play this puzzle online at the Daily Sudoku site
Before solving it with a forcing chaim I noticed that a 6 at r9c9 is disastrous, in that there is no place for a 6 allowed in box 7, Since draw/play could not find this it can't be too obvious yet it is fairly easy to spot- so what is this elimination called?
If this is the wrong section to contribute this I will delete it if advised! |
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TKiel
Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI
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| Posted: Mon Aug 20, 2007 3:13 pm Post subject: |
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This is known by many names. I call it multi-coloring, since it involves more that one strongly linked chain. The chains are connected by a weak link.
In this configuration, it would exclude the <6> from r9c9.
| Code: |
*--------------------------------------------------------------------*
| 678B | | 678b |
| 267A 26789 | | 678 |
| | | |
|----------------------+----------------------+----------------------|
| | 346 367 | 367 |
| | | |
| | 346 3678 | 367 |
|----------------------+----------------------+----------------------|
| 3689 | 236 | 3689 |
| 367 | 236 | 367 |
| 67a 36789 | 36 | 36789 -678 |
*--------------------------------------------------------------------*
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In this configuration, it would exclude the <6> from r1c3 & r2c7.
| Code: |
*--------------------------------------------------------------------*
| -678 | | 678b |
| 267a 26789 | |-678 |
| | | |
|----------------------+----------------------+----------------------|
| | 346 367 | 367 |
| | | |
| | 346 3678 | 367 |
|----------------------+----------------------+----------------------|
| 3689 | 236 | 3689 |
| 367 | 236 | 367 |
| 67A 36789 | 36 | 36789 67B |
*--------------------------------------------------------------------*
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I would configure it like this, which would place the <6> in r1c9, effectively accomplishing both steps above in one move.
| Code: |
*--------------------------------------------------------------------*
| 678B | | 678b |
| 267a 26789 | | 678B |
| | | |
|----------------------+----------------------+----------------------|
| | 346 367 | 367 |
| | | |
| | 346 3678 | 367 |
|----------------------+----------------------+----------------------|
| 3689 | 236 | 3689 |
| 367 | 236 | 367 |
| 67A 36789 | 36 | 36789 67B |
*--------------------------------------------------------------------*
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Others may call it fork, color wing, two-string kite (aaaaaaah!), skyscraper (aaaaaaah!), turbot fish, etc. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Mon Aug 20, 2007 3:54 pm Post subject: |
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| Tracy, your first two examples are pretty conventional strong links but I don't have a clue about the third, with three capital "Bs" and one lower case, with that r2c7 seemingly sitting in limbo. |
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TKiel
Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI
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| Posted: Mon Aug 20, 2007 4:19 pm Post subject: |
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| The third example shows B as a peer of both A & a, which means that b must be where the digit is. |
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Mogulmeister
Joined: 03 May 2007
Posts: 1151
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| Posted: Tue Aug 21, 2007 11:13 pm Post subject: |
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| Actually, I like Havard's descriptions of "skyscraper" and "2 string kite". For the visual amongst us they are very allegorical and work well. |
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