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How difficult is this puzzle?

 
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sat Jan 19, 2008 10:43 pm    Post subject: How difficult is this puzzle? Reply with quote
Code:
Puzzle: M5361273sh(67)
+-------+-------+-------+
| . . 8 | . 4 . | . . . |
| . . . | . 1 . | . . 3 |
| 7 . 9 | . . . | 4 . 1 |
+-------+-------+-------+
| . . 2 | . . 5 | . 9 . |
| . . . | 1 . 6 | . 8 . |
| 4 . 6 | 7 . . | . 1 . |
+-------+-------+-------+
| 5 . 1 | . . . | . 4 . |
| . . 4 | 9 . . | . . 2 |
| . . . | . 8 . | . . . |
+-------+-------+-------+

Should be relatively tough, if you look at the Menneske rating of 67.

So far as I can see, Menneske rates as "super hard" any puzzle that cannot be solved by a list of methods. So far as I can see this list does not include XY-wings and XYZ-wings. (Now, I realize why I like these puzzles so much. His list includes X-wings, swordfish, etc., so the fishes do not show up in the "super hard" category. They are "very hard".)

(Good news for Marty, too. He is an avid fisherman, except when it comes to Sudoku.)

Then, it seems, he starts testing to see how many of the remaining candidates need to be eliminated to solve the puzzle. IMHO, this is a fool's game: How can you judge the difficulty of a puzzle that you cannot solve? Particularly, if you are trying to rank its difficulty vs. other unsolved puzzles.

This puzzle: As my teachers used to say, it is easy, had you been paying attention. Quite simply, it can be cracked by a simple method Menneske does not use.

(By the way, knowing techniques that the puzzle makers do not test for is an "advantage", in that you can solve puzzles they rate as very difficult.)

Keith
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ravel



Joined: 21 Apr 2006
Posts: 536
PostPosted: Sun Jan 20, 2008 12:21 am    Post subject: Reply with quote
Maybe the most complex thing, i was concerned with sudoku is rating. If you want to know, how hard a puzzle is, i have to ask you, which techniques you know and in which order you try to apply them, before i can answer. And also this is roughly speaking. It happened to me, that i saw a hidden quad before a naked single.

I think, a good way is to say, this puzzle can be solved with this pool of techniques (what you have on this site).
As far as i know, there is no program available, that has w-wings, special UR eliminations and other techniques implemented, that can be spotted relatively easy. But i also like that, otherwise each user could get a better solution than mine just with a click Wink
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Victor



Joined: 29 Sep 2005
Posts: 207
Location: NI
PostPosted: Sun Jan 20, 2008 7:41 pm    Post subject: Reply with quote
Actually, much like Storm_norm's puzzle of a day or two ago - solved by colouring alone. Still nice. One of the reasons why I quite like Menneske's is the mild unpredictability in difficuly level.
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sun Jan 20, 2008 8:09 pm    Post subject: Reply with quote
Victor,

This one is easily solved by a remote pair. (Which is coloring of a sort.)

Keith
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Asellus



Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
PostPosted: Mon Jan 21, 2008 2:01 am    Post subject: Reply with quote
It can also be solved by the probably even more basic Skyscraper (on <5> in r38), which is also a form of coloring.
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storm_norm



Joined: 18 Oct 2007
Posts: 1741
PostPosted: Mon Jan 21, 2008 3:35 am    Post subject: Reply with quote
hmm, all this discussion on techniques is begging for a poll.

maybe someone wants to start a thread...something along the lines of:

which techniques you prefer to apply first.

maybe a poll that will allow the user to give values to the techniques according to preference. for example:

I look for these techniques in this order

1. coloring ( includes skyscraper, kite, etc )
2. x-wings
3. xy-wings
4. URs
5. xy-chains
6. swordfish
7. xyz-wings
8. finned x-wings
9. APE
10. medusa

tally the polls to find a score on each technique. obviously, the lower the average is the higher on the list it is, and therefore is prefered more as a starting approach.

or maybe this is a little far fetched, lol.
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