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May 9th a real cracker...!

 
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BobbieTheWiz
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PostPosted: Tue May 09, 2006 4:19 pm    Post subject: May 9th a real cracker...! Reply with quote

I spent a couple of hours with the May 9th puzzle. I had to crack 3 (three) X-wings (a.k.a unique rectangles) to solve it.

My question is: did I go about it the wrong way? Started with the wrong one, perhaps? Or was it in fact necessary to find those three different X-wings to crack this puzzle? Would be nice to hear other opinions about this.
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Marty R.



Joined: 12 Feb 2006
Posts: 5061
Location: Rochester, NY, USA

PostPosted: Tue May 09, 2006 4:56 pm    Post subject: Re: May 9th a real cracker...! Reply with quote

BobbieTheWiz wrote:
I spent a couple of hours with the May 9th puzzle. I had to crack 3 (three) X-wings (a.k.a unique rectangles) to solve it.

My question is: did I go about it the wrong way? Started with the wrong one, perhaps? Or was it in fact necessary to find those three different X-wings to crack this puzzle? Would be nice to hear other opinions about this.

I haven't done the puzzle, so I can't comment on the specifics. However, X-Wings and unique rectangles are two different things. Here is Keith's excellent primer on rectangles:

http://www.dailysudoku.co.uk/sudoku/forums/viewtopic.php?t=744

If you arrived at the correct solution, I don't think you went about it the wrong way, although it's quite possible that you didn't see the quickest way. From reading this forum, I quickly learned that there are multiple approaches and techniques that will lead to the correct solution on many, if not most, puzzles.
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Angel



Joined: 26 Mar 2006
Posts: 31

PostPosted: Tue May 09, 2006 5:18 pm    Post subject: Reply with quote

Bobbie, I needed one X-wing to complete the puzzle.
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keith



Joined: 19 Sep 2005
Posts: 3136
Location: near Detroit, Michigan, USA

PostPosted: Tue May 09, 2006 5:42 pm    Post subject: Not yet complete ... Reply with quote

I have not finished the puzzle, but there is a Unique Rectangle that has two types of eliminations.

Keith
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BobbieTheWiz
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PostPosted: Tue May 09, 2006 5:45 pm    Post subject: wings Reply with quote

Thanks, Marty, for clearing that up. I meant I needed to crack three different X-wings. And thanks Angel, for your reply. I think I know what that singular X-wing was. Involving 2:s, right? Smile
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Marty R.



Joined: 12 Feb 2006
Posts: 5061
Location: Rochester, NY, USA

PostPosted: Tue May 09, 2006 6:27 pm    Post subject: Reply with quote

I have since done the puzzle and the standard techniques of pairs, triples, hidden singles and locked candidates were enough to complete it.
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Angel



Joined: 26 Mar 2006
Posts: 31

PostPosted: Tue May 09, 2006 6:39 pm    Post subject: Reply with quote

Bobbie - Yes!

Marty - I'll need to try again, the way I did it definitely needed the X-wing!

Keith - I'm not really into URs, so didn't notice anything!
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Korky



Joined: 29 Mar 2006
Posts: 13
Location: Sheffield, UK

PostPosted: Thu May 11, 2006 12:03 am    Post subject: Reply with quote

I'm a little bemused by the theme of this thread. The puzzle is solved without the use of any of the techniques mentioned.
After you have entered all of the "obvious " numbers, you deduce, by elimination, that the numbers in R1C1 and R2C1 must be 2 and 6. You then observe where in column 9 where 2,5 and 7 can't be, therefore where they must be, and what numbers must be where the aforesaid 2,5 and 7 aren't.

Are you with me so far?
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keith



Joined: 19 Sep 2005
Posts: 3136
Location: near Detroit, Michigan, USA

PostPosted: Thu May 11, 2006 12:13 am    Post subject: Reply with quote

Korky,

What is happening here is that the previous two "very difficult" puzzles on this site required X-wings, and also had Unique Rectangles. Before that, no puzzle needed these techniques.

So, everyone was looking for the X-wings and rectangles in this puzzle! Which I think is OK. Why ignore the obvious rectangle, even though there may yet be a difficult hidden single or pair?

Keith
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BobbieTheWiz
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PostPosted: Thu May 11, 2006 1:46 pm    Post subject: Reply with quote

Korky may be "bemused", but there are actually many ways to crack a puzzle. I was looking for X-wings (for the exact reason Keith just brought up) and found them... and, sure, this may very well be somewhat like... eh... eating food with sticks when there are knives, forks and spoons avaiable... but that's fine with me! Happy sudoking, everyone! Cool
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Glassman



Joined: 21 Oct 2005
Posts: 50
Location: England

PostPosted: Thu Jun 22, 2006 10:54 am    Post subject: Reply with quote

Marty R. wrote:
I have since done the puzzle and the standard techniques of pairs, triples, hidden singles and locked candidates were enough to complete it.

Same here I just looked for and found pairs and triples as normal, although there were many more than usual, many interlocking. The puzzle seemed to solve with no difficulty, and without having to resort to "uniquity", i.e. by assuming uniqueness of the solution, which would have allowed me to eliminate the 5 from r8c8 and r9c8.

Glassman Cool
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