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garytorborg
Joined: 19 Jan 2011
Posts: 28
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 Posted: Tue Mar 22, 2011 2:33 pm Post subject: Another too hard puzzle |
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Thanks to your help, I've been able to use some of my newly learned techniques to solve more and more of the "fiendish" puzzles I encounter. However, I am stuck again on one:
| Code: |
+---------------+----------------+-------------+
| 5 146 149 | 279 14 27 | 3 467 8 |
| 3 7 169 | 8 145 145 | 19 2 46 |
| 149 8 2 | 79 3 6 | 19 5 47 |
+---------------+----------------+-------------+
| 2 45 3 | 6 7 45 | 8 9 1 |
| 7 9 14 | 14 2 8 | 6 3 5 |
| 6 15 8 | 15 9 3 | 27 47 247 |
+---------------+----------------+-------------+
| 8 2 57 | 3 6 57 | 4 1 9 |
| 14 3 14567 | 2457 145 9 | 257 8 267 |
| 149 146 14579 | 2457 8 12457 | 257 67 3 |
+---------------+----------------+-------------+
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Play this puzzle online at the Daily Sudoku site
This was kind of a wild one so far: basics included a whopping *5* naked pairs, 2 naked triples, and a quad. There were/are 2 x-wings and 1 xy-wing that have resulted in several eliminations. Two chains have each removed a single candidate each. Chains involving the several cells with "14" in them all lead to dead ends (unless I'm doing something wrong). What am I missing? Thanks in advance. |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Tue Mar 22, 2011 3:16 pm Post subject: |
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There's a W-Wing that'll help you out ... for awhile.
| Code: | +-----------------------------------------------------------------------+
| 5 146 149 | 279 14 27 | 3 467 8 |
| 3 7 169 | 8 145 145 | 19 2 46 |
| 149 8 2 | 79 3 6 | 19 5 47 |
|-----------------------+-----------------------+-----------------------|
| 2 45 3 | 6 7 45 | 8 9 1 |
| 7 9 14 | 14 2 8 | 6 3 5 |
| 6 15 8 | 15 9 3 | 27 47 247 |
|-----------------------+-----------------------+-----------------------|
| 8 2 57 | 3 6 57 | 4 1 9 |
| 14 3 14567 | 2457 145 9 | 257 8 267 |
| 149 146 14579 | 2457 8 12457 | 257 67 3 |
+-----------------------------------------------------------------------+
# 67 eliminations remain
W-Wing: (1=4)r1c5 - r1c23 = r3c1 - (4=1)r8c1 => r8c5<>1
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garytorborg
Joined: 19 Jan 2011
Posts: 28
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| Posted: Tue Mar 22, 2011 4:14 pm Post subject: |
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Indeed, that helped a great deal! Thank you! Now, the puzzle is at this position:
| Code: |
+--------------+------------+-------------+
| 5 146 149 | 79 14 2 | 3 467 8 |
| 3 7 169 | 8 145 45 | 19 2 46 |
| 149 8 2 | 79 3 6 | 19 5 47 |
+--------------+------------+-------------+
| 2 45 3 | 6 7 45 | 8 9 1 |
| 7 9 14 | 14 2 8 | 6 3 5 |
| 6 15 8 | 15 9 3 | 27 47 247 |
+--------------+------------+-------------+
| 8 2 5 | 3 6 7 | 4 1 9 |
| 14 3 1467 | 245 45 9 | 257 8 267 |
| 49 46 479 | 245 8 1 | 257 67 3 |
+--------------+------------+-------------+
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Play this puzzle online at the Daily Sudoku site
It's now to a point where it's giving me the "hint" of a 1 in R8C1, but I have no idea how it's arriving at that (i.e. how is the 4 being eliminated there). Any more ideas? |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Tue Mar 22, 2011 4:55 pm Post subject: |
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| Look for a quad in row 9. |
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garytorborg
Joined: 19 Jan 2011
Posts: 28
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| Posted: Tue Mar 22, 2011 5:10 pm Post subject: |
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| Marty R. wrote: | | Look for a quad in row 9. |
Aha. The quad also exposes a hidden pair (R9C47) of "25"s. That solves R8C1 (1) and eliminates 4 from R8C3.
Thanks so far... still looking for the next step. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Tue Mar 22, 2011 5:32 pm Post subject: |
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| Are you familiar with Hidden URs? One on the 25 UR will remove the 5 from r8c7, exposing a Type 4 UR on 27. |
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garytorborg
Joined: 19 Jan 2011
Posts: 28
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| Posted: Tue Mar 22, 2011 6:59 pm Post subject: |
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| Marty R. wrote: | | Are you familiar with Hidden URs? One on the 25 UR will remove the 5 from r8c7, exposing a Type 4 UR on 27. |
Thank you! That solved it. I am familiar with URs, but I don't quite understand the "hidden" UR business. Aren't they all "hidden" to some degree when more than one of the cells contain one or more additional candidates? (i.e. Type 3 or Type 4). I am not certain how the rectangle of 25s eliminates the 5 in r8c7, but when I removed the 5 from there, I saw the Type 4 UR on 27 immediately, made the appropriate eliminations, and the rest was singles.
So could you help me further with the "hidden" UR part of this solution?
Thanks. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Tue Mar 22, 2011 7:21 pm Post subject: |
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There are a few different Hidden Rectangles. This type occurs when you have both bivalue cells in the "floor" cells and polyvalue cells in the "roof" cells. If one of the candidates is a strong link in the floor and roof cells, then you can remove the other candidate from the polyvalue cell in the other line.
In this case, there are only two 2s in column 4, so you remove the 5 from r7c8. It's not needed, but there are only two 5s in column 7, so the 2 is removed from r8c4.
Here's a link to one explanation. You can probably find others with a search.
http://www.sudokuwiki.org/Hidden_Unique_Rectangles |
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garytorborg
Joined: 19 Jan 2011
Posts: 28
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| Posted: Tue Mar 22, 2011 7:51 pm Post subject: |
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| Thanks, Marty, and all. That makes sense. |
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