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sheryl
Joined: 24 Sep 2007
Posts: 64
Location: New York
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 Posted: Tue Aug 05, 2008 6:16 pm Post subject: Some new sites |
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i don't know if anyone knows of these sites, but they always have a daily puzzle that is as hard if not (often is) harder than the VH. I'd love someone's impression. Todays Fiendish at this site was not doable for me. (without guessing).
http://www.playr.co.uk/sudoku/index.php?class=5
Also another site is
http://brainbashers.com/sudoku.asp
select the SUPER HARD from the drop down menu. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Tue Aug 05, 2008 7:09 pm Post subject: Re: Some new sites |
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| sheryl wrote: | Todays Fiendish at this site was not doable for me. (without guessing).
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I can see why ...
A very tough puzzle.
Where basics end:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 468 46 5 | 2 7 89 | 1 3 469 |
| 2468 246 1 | 5 3 89 | 7 49 469 |
| 3 7 9 | 4 1 6 | 2 8 5 |
+--------------------------+--------------------------+--------------------------+
| 24 124 37 | 17 9 34 | 6 5 8 |
| 49 8 37 | 6 5 2 | 39 1 47 |
| 5 149 6 | 17 8 34 | 39 247 247 |
+--------------------------+--------------------------+--------------------------+
| 1 5 8 | 9 2 7 | 4 6 3 |
| 679 69 2 | 3 4 5 | 8 79 1 |
| 79 3 4 | 8 6 1 | 5 279 279 |
+--------------------------+--------------------------+--------------------------+
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There is a kite in 4, row 5 col 8 - or -
An xy-wing 79-49-47 (col 1, row 5), removes 7 from r9c9
a UR 79 r89c18 with strong link 7 in col 1 (removes 7 from r9c8)
But, alas, it is either xy-chains here
| Code: |
+--------------------------+--------------------------+--------------------------+
| 468 46 5 | 2 7 89 | 1 3 469 |
| 268 246 1 | 5 3 89 | 7 49 469 |
| 3 7 9 | 4 1 6 | 2 8 5 |
+--------------------------+--------------------------+--------------------------+
| 24 124 37 | 17 9 34 | 6 5 8 |
| 49 8 37 | 6 5 2 | 39 1 47 |
| 5 149 6 | 17 8 34 | 39 24 247 |
+--------------------------+--------------------------+--------------------------+
| 1 5 8 | 9 2 7 | 4 6 3 |
| 69 69 2 | 3 4 5 | 8 7 1 |
| 7 3 4 | 8 6 1 | 5 29 29 |
+--------------------------+--------------------------+--------------------------+
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or, using a possible DP 68 89 69 in r12c169:
either r12c1 is 2 or 4 (which gives a virtual naked pair together with r4c1 and) thus r5c1=9 and r5c7=3
or r12c9=4 (which gives r6c8=4 and) thus r6c6=3.
This means at least one of r5c7,r6c6 must be 3 and we can remove 3 from r6c7 |
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sheryl
Joined: 24 Sep 2007
Posts: 64
Location: New York
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| Posted: Tue Aug 05, 2008 7:17 pm Post subject: |
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[quote] | Quote: | There is a kite in 4, row 5 col 8 - or -
An xy-wing 79-49-47 (col 1, row 5), removes 7 from r9c9 |
I followed you to there, but i don't see the strong link here
| Quote: | | a UR 79 r89c18 with strong link 7 in col 1 (removes 7 from r9c8) |
there is a strong link on 7s in col. 1 but there is a strong link on 7s in col. 8 too. how did you determine that the 7 in r9c8 was removable?? |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Tue Aug 05, 2008 7:35 pm Post subject: |
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The 7 in r6c8 prevents a strong link in col 8.
If that 7 were not there, it would be possible to remove 7 from r8c1 as well.
How to remove 7 from r9c8?
if r9c8=7 then r9c1=9 then (strong link col 1) r8c1=7 then r8c8=9 which is a DP.
In all "diagonal" URs (a,b) with strong link in "a", remove a from the "other side" (i.e. from the multi-value cell that is not part of the strong link). |
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sheryl
Joined: 24 Sep 2007
Posts: 64
Location: New York
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| Posted: Tue Aug 05, 2008 8:07 pm Post subject: |
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The 7 in r6c8 prevents a strong link in col 8.
If that 7 were not there, it would be possible to remove 7 from r8c1 as well.
| Quote: | How to remove 7 from r9c8?
if r9c8=7 then r9c1=9 then (strong link col 1) r8c1=7 then r8c8=9 which is a DP.
In all "diagonal" URs (a,b) with strong link in "a", remove a from the "other side" (i.e. from the multi-value cell that is not part of the strong link). |
i don't have a 7 in r6c8 just a 24, i removed it when i did the xy wing taking the 7 from r9c9 because that left box 9 to be the only place for a 7 in col 8 so i removed the 7 from box 6.
yes i know about the type 6A URs but i couldn't make the strong link because i have a strong link on the 7s in col. 1, r.8, and col. 8.
oh well. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Tue Aug 05, 2008 8:14 pm Post subject: Re: Some new sites |
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Sheryl, I go to the playr.co.uk on occasion to play the Fiendish and even try the Extreme if I feel really brave (or stupid). Also, I go the the BrainBashers daily to play the Super Hard puzzles. In fact, I found todays, August 5, to be very interesting.
Ted |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Tue Aug 05, 2008 8:45 pm Post subject: |
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| sheryl wrote: |
yes i know about the type 6A URs but i couldn't make the strong link because i have a strong link on the 7s in col. 1, r.8, and col. 8.
oh well. |
Sheryl, I see that you are already further in the puzzle and there is indeed another strong link(7) in col 8. So much better! You can remove 7 from r9c8 AND r8c1!!!
The position after kite, xy-wing and cleanup:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 468 46 5 | 2 7 89 | 1 3 469 |
| 268 246 1 | 5 3 89 | 7 49 469 |
| 3 7 9 | 4 1 6 | 2 8 5 |
+--------------------------+--------------------------+--------------------------+
| 24 124 37 | 17 9 34 | 6 5 8 |
| 49 8 37 | 6 5 2 | 39 1 47 |
| 5 149 6 | 17 8 34 | 39 24 247 |
+--------------------------+--------------------------+--------------------------+
| 1 5 8 | 9 2 7 | 4 6 3 |
| 6-79 69 2 | 3 4 5 | 8 79 1 |
| 79 3 4 | 8 6 1 | 5 2-79 29 |
+--------------------------+--------------------------+--------------------------+
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The logic by which the sevens are removed does not depend on the absence or presence of other strong or weak links.
I did a writeup on my homegrown method for some "UR with single strong link" patterns in the
Solving techniques, and terminology section of our forum.
Of course, with the extra 7s gone from col 8 and row 9, it is now a type 6 (diagonal UR with x-wing) |
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sheryl
Joined: 24 Sep 2007
Posts: 64
Location: New York
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| Posted: Tue Aug 05, 2008 9:11 pm Post subject: |
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Ted, I found today's SH fairly easy but as i said, i really had (and am still Having) trouble with today's Fiendish (and i don't think i would ever be able to do the extreme--because it's 50/50 whether i can do the Fiendish.)
Nataraj--I couldn't really follow your explanation. I have a really difficult time with those (??) AIC things. the ones where you have to go, if this is this, then that is that and this can't be such and such so that one has to be ?. So when the puzzles come down to that it's over for me. i do understand the deadly pattern but not that way of getting there. and in this particular puzzle i see where the deadly pattern can be, but i just don't understand the elimination. sometimes i make a guess (or what i like to think is an educated guess) and many times it's right, but i've been wrong too, so it's still guessing. oh well, maybe someday. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Tue Aug 05, 2008 9:13 pm Post subject: |
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I play puzzles from both sites, Vanhegan and Brain Bashers. Another site whose puzzles are played by a number of members here is Menneske,
http://www.menneske.no/sudoku/eng/ |
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sheryl
Joined: 24 Sep 2007
Posts: 64
Location: New York
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| Posted: Tue Aug 05, 2008 10:02 pm Post subject: |
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thanks for the site tip, Marty. i'm going to try one now. this was at the bottom of the puzzle that comes up when i click on your link.
Showing puzzle number: 616563
Puzzletype: Symmetrical Sudoku
Startnumbers: 32
Difficulty: Very easy (0)
what does startnumbers: 32 mean? i clicked on SuperHard and that one says, StartNumbers: 27, difficulty 40. others are different. any ideas? |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Tue Aug 05, 2008 10:33 pm Post subject: |
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| sheryl wrote: | thanks for the site tip, Marty. i'm going to try one now. this was at the bottom of the puzzle that comes up when i click on your link.
Showing puzzle number: 616563
Puzzletype: Symmetrical Sudoku
Startnumbers: 32
Difficulty: Very easy (0)
what does startnumbers: 32 mean? i clicked on SuperHard and that one says, StartNumbers: 27, difficulty 40. others are different. any ideas? |
Startnumbers is number of initial givens.
Difficulty level: Has been discussed before, no one knows. Here's what I think:
Menneske's solver does only basic moves, no wings or fish, etc. If basic moves solve a puzzle, it has a score of zero. If not, he has a scoring system that looks at all bivalue cells. If a guess in any cell solves the puzzle, I think it becomes a Very Hard with a rating of (0). If not, it is a Super Hard. The difficullty level seems to depend on how unlikely it is that random guesses will solve the puzzle.
As I have said before, how can you rank the difficulty of a puzzle you cannot systematically solve?
Anyway, the Menneske puzzles are really great. Choose "Super Hard". If you get a "Very Hard (0)", go for it! From there up to about Super Hard (17) you can use wings (including W and M) to solve most of them.
Above Super Hard (20) it gets more difficult. Above (30), I usually don't bother.
What puzzles would you take on a desert island? I will be away for three weeks. I have printed a month (April 2008) of Brain Basher's Super Hard, plus 50 Menneskes ranging from Very Hard (0) to Super Hard (less than 30). All the Menneskes were obtained by asking for a Super Hard.
Best wishes,
Keith. |
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sheryl
Joined: 24 Sep 2007
Posts: 64
Location: New York
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| Posted: Tue Aug 05, 2008 10:50 pm Post subject: |
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| Quote: | | What puzzles would you take on a desert island? I will be away for three weeks. I have printed a month (April 2008) of Brain Basher's Super Hard, plus 50 Menneskes ranging from Very Hard (0) to Super Hard (less than 30). All the Menneskes were obtained by asking for a Super Hard. |
i think i would take the ones you mentioned plus the playr. one i listed above. there is a site called KrazyDad, and he does booklets of puzzles, but i've been pretty unsuccessful in solving them so i probably wouldn't take them, but maybe you can. |
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