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crunched
Joined: 05 Feb 2008
Posts: 168
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 Posted: Fri Apr 11, 2008 12:15 am Post subject: Wednesday, April 10, 2008 Hard not Easy |
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| This Hard puzzle was one of the tougher hard ones for me in recent memory. Took me a long time---like a couple hours or more. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Apr 11, 2008 4:59 am Post subject: |
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After some basics, my position was:
| Code: |
+------------+--------------+--------------+
| 25 279 159 | 256 1247 8 | 3467 467 34 |
| 3 4 15 | 56 17 567 | 9 678 2 |
| 6 27 8 | 23 2347 9 | 5 47 1 |
+------------+--------------+--------------+
| 7 3 4 | 9 56 1 | 2 56 8 |
| 9 5 6 | 28 28 4 | 1 3 7 |
| 1 8 2 | 7 56 3 | 46 4569 49 |
+------------+--------------+--------------+
| 8 269 7 | 1 23 26 | 34 49 5 |
| 4 1 3 | 58 9 57 | 78 2 6 |
| 25 269 59 | 4 2378 267 | 378 1 39 |
+------------+--------------+--------------+
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Play this puzzle online at the Daily Sudoku site
I don't know if you're familiar with Unique Rectangles, but there's what's called a Type 1 Rectangle on 56 in boxes 5 and 6. The 56 have to be removed from r6c8 and that solves the puzzle. I'm not sure if that rectangle was needed, but I saw it and used it.
If you're not familiar with rectangles, you can find an introduction here:
http://www.sudoku.com/boards/viewtopic.php?p=29105#29105 |
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tippwell
Joined: 19 Sep 2007
Posts: 9
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| Posted: Sat Apr 12, 2008 9:28 am Post subject: |
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somewhere I got the impression that URs use the fact that the solution should be unique (but conceivably it might not be) so I try to avoid them. Or is this being pedantic?
in Marty's layout, in box 9, the 34, 49, 39 means the 3 comes out of the 378, taking the 7 out of 3467 in box 3.
Also the only 2s in col 6 are in box 8, meaning the other 2s in that box can go.
I haven't worked it through, but suspect that will be enough to solve it. |
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tippwell
Joined: 19 Sep 2007
Posts: 9
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| Posted: Sat Apr 12, 2008 10:12 am Post subject: |
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| and now noticed there was only one 3 in column 4 (in box 2). |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat Apr 12, 2008 12:19 pm Post subject: |
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You don't need URs for a Hard puzzle. They belong to the VHs that we used to get  Once I spotted the Hidden Pair of <89> in C2Box1 it was all singles and pairs. |
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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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| Posted: Sat Apr 12, 2008 2:04 pm Post subject: not easy |
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There is a 349 xy-wing in boxes 6&9 which eliminates the 4 from R6C7 and solves the puzzle. Yes, this is equal to many VH's.
Earl |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat Apr 12, 2008 3:05 pm Post subject: |
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| I probably sound like a Friday night Saturday morning curmudgeon - but the Hard ones don't need wings either - just pairs, triples, (quads even) and line box eliminations. This one just needed one triple and a hidden pair. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat Apr 12, 2008 3:29 pm Post subject: |
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| Quote: | | somewhere I got the impression that URs use the fact that the solution should be unique (but conceivably it might not be) so I try to avoid them. Or is this being pedantic? |
Yes, URs are based on the assumption that it has a unique solution and it's stated that all puzzles here have just one solution.
As mentioned by other posters, the UR is not needed and the puzzles are generally solvable by using subsets and locked candidates. |
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crunched
Joined: 05 Feb 2008
Posts: 168
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| Posted: Sat Apr 12, 2008 7:41 pm Post subject: |
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Thanks for pointing out the UR. I now understand that "tool".
I agree that the puzzle did not *need* a UR to solve, nor did it need any wings. I solved it without them, but it took a long time---a very long time.
I guess my point was that wingless puzzles are not always a snap. Some puzzles don't seem to have much in the way of pairs and triples. Those are the ones that take me a long time.
On the other hand, there are hard puzzles with lots of pairs and triples that quickly solve.
Do some of you consider using URs or wings to be cheating if used in anything less than a VH? |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Apr 12, 2008 8:05 pm Post subject: |
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| crunched wrote: | Thanks for pointing out the UR. I now understand that "tool".
Do some of you consider using URs or wings to be cheating if used in anything less than a VH? |
"Cheating" is too strong a term. It's a personal preference. Generally, if I know a puzzle can be solved using particular techniques, I will stick to those techniques.
Keith
Last edited by keith on Sat Apr 12, 2008 10:29 pm; edited 1 time in total |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat Apr 12, 2008 9:23 pm Post subject: |
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| Quote: | | Do some of you consider using URs or wings to be cheating if used in anything less than a VH? |
I'd say it's like using those sonic devices for fishing - it's efficiency vs sport. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Apr 12, 2008 10:33 pm Post subject: |
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| cgordon wrote: | | I'd say it's like using those sonic devices for fishing ... |
Fishing is different. We use dynamite.  |
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