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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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 Posted: Sun Jan 06, 2008 11:28 am Post subject: stuck |
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| Code: | 18 238 1238 | 5 36 4 | 278 267 9
6 24 7 | 89 18 19 | 3 245 45
59 59 348 | 2 36 7 | 48 46 1
------------------------+-------------------------+------------------
2 6 148 | 489 1458 159 | 1457 1457 3
18 348 5 | 348 7 2 | 9 14 6
79 79 134 | 6 145 135 | 145 8 2
------------------------+-------------------------+------------------
3 125 6 | 7 245 8 | 1245 9 45
57 12578 9 | 34 245 35 | 6 1245 78
4 2578 28 | 1 9 6 | 25 3 78
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this is where I am stuck on last week's extreme # 67
http://www.sudoku.org.uk/PrintWeeklySudoku.asp?number=67 |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Sun Jan 06, 2008 2:43 pm Post subject: |
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Nice puzzle. Here is a solution with many techniques.
| Code: | *--------------------------------------------------------------------*
| 18 238 1238 | 5 36 4 | 278 267 9 |
| 6 24 7 |&89 &18 &19 | 3 245 45 |
|@59 @59 348 | 2 36 7 | 48 46 1 |
|----------------------+----------------------+----------------------|
| 2 6 148 |&489 &1458 &159 | 1457 1457 3 |
| 18 348 5 | 348 7 2 | 9 14 6 |
|@79 @79 134 | 6 145 135 | 145 8 2 |
|----------------------+----------------------+----------------------|
| 3 125 6 | 7 245 8 | 1245 9 45 |
|@57 #12578 9 | 34 245 35 | 6 1245 #78 |
| 4 #2578 28 | 1 9 6 | 25 3 #78 |
*--------------------------------------------------------------------* |
First some uniqueness eliminations.
UR 78 # in r89c29 with strong links for 8 in r8 and 7 in r9 eliminates 7 in r9c2 and 8 in r8c2.
DP 59-79-57 @ in r368c12 eliminates 57 from r8c2.
DP 189 & in r24c456: Either r5c4=8 => r5c1=1 or r6c56=1. In both cases r6c3<>1.
Brings you here.
| Code: | *-----------------------------------------------------------*
| 18 238 1238 | 5 36 4 | 278 267 9 |
| 6 24 7 | 89 18 19 | 3 245 45 |
| 5 9 348 | 2 36 7 | 48 46 1 |
|-------------------+-------------------+-------------------|
| 2 6 148 | 489 1458 159 | 1457 1457 3 |
| 18 348 5 | 348 7 2 | 9 14 6 |
| 9 7 34 | 6 145 135 | 145 8 2 |
|-------------------+-------------------+-------------------|
| 3 #125 6 | 7 #245 8 | #1245 9 45 |
| 7 #12 9 | 34 #245 35 | 6 1245 8 |
| 4 258 28 | 1 9 6 | 25 3 7 |
*-----------------------------------------------------------* |
Either r8c2=1 => r7c7=1 or r8c2=2 => r7c5=2.
In both cases r7c7<>2.
This opens an x-wing, followed by 2 xyz-wings, later a kite.
| Code: | *--------------------------------------------------*
| 1 38 28 | 5 36 4 | 27 67 9 |
| 6 24 7 | 89 18 19 | 3 24 5 |
| 5 9 34 | 2 36 7 | 8 46 1 |
|----------------+----------------+----------------|
| 2 6 1 | 89 458 59 | 457 57 3 |
| 8 34 5 | 34 7 2 | 9 1 6 |
| 9 7 34 | 6 145 135 | 45 8 2 |
|----------------+----------------+----------------|
| 3 25 6 | 7 25 8 | 1 9 4 |
| 7 1 9 | 34 245 35 | 6 25 8 |
| 4 58 28 | 1 9 6 | 25 3 7 |
*--------------------------------------------------*
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Here a 9-cell xy-chain eliminates 2 from r1c3. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sun Jan 06, 2008 9:50 pm Post subject: |
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Ravel,
ok, I understand the UR on 78 and the eliminations, I should have seen that.
but the next one you did, the 57-79-57 DP. that is very interesting. not seeing this particular situation as a DP in the past, my question is, the DP exists if r8c2 is 57?? and does this particular situation have a name, because it looks nice, almost like a three tiered UR? |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Jan 06, 2008 10:20 pm Post subject: |
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I wouldn't have spotted it, but can certainly see the DP in the first stack, with the two solutions in the next two stacks.
| Code: |
+---------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| 59 59 . | 5 9 . | 9 5 . |
+---------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| 79 79 . | 9 7 . | 7 9 . |
+---------+-------+-------+
| . . . | . . . | . . . |
| 57 57 . | 7 5 . | 5 7 . |
| . . . | . . . | . . . |
+---------+-------+-------+
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Play this puzzle online at the Daily Sudoku site |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Mon Jan 07, 2008 8:56 am Post subject: |
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| Here are two threads about deadly patterns, by Myth Jellies and RW . A great spot was the one found by Asellus here. |
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