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Stuart puzzle May 25 diabolical spoiler warning

 
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Glassman



Joined: 21 Oct 2005
Posts: 50
Location: England

PostPosted: Sun May 27, 2007 9:21 pm    Post subject: Stuart puzzle May 25 diabolical spoiler warning Reply with quote

Code:

+---------------+------------+---------------+
| 3    48  1578 | 67 2   14  | 49   146 5689 |
| 1247 6   157  | 9  147 8   | 3    14  25   |
| 124  9   18   | 5  146 3   | 24   7   268  |
+---------------+------------+---------------+
| 8    127 3    | 67 167 129 | 5    29  4    |
| 9    12  4    | 8  5   12  | 6    3   7    |
| 5    27  6    | 3  47  249 | 8    29  1    |
+---------------+------------+---------------+
| 146  3   19   | 2  8   7   | 149  5   69   |
| 17   5   2    | 4  9   6   | 17   8   3    |
| 467  48  789  | 1  3   5   | 2479 46  269  |
+---------------+------------+---------------+

Play this puzzle online at the Daily Sudoku site

I'm really stuck on this. The hint is to eliminate the 6 at r1c4, but I can't see how.

Help

Glassman Cool
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keith



Joined: 19 Sep 2005
Posts: 3173
Location: near Detroit, Michigan, USA

PostPosted: Sun May 27, 2007 9:39 pm    Post subject: Reply with quote

Glassman,

At the risk of irritating you, the Type 3 UR in R46C68 says R5C6 is <2>.

Otherwise, an XY-wing 18-48-14 takes out <1> from R1C3 an R3C5.

Then, there is another XY-wing, and an X-wing ...

Neat puzzle!

But, I do not see how to complete the puzzle without a chain ...

Keith
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Mogulmeister



Joined: 03 May 2007
Posts: 695

PostPosted: Sun May 27, 2007 10:13 pm    Post subject: Reply with quote

Glassman,

I don't see it straight away either - I do see an XY wing though.
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Mogulmeister



Joined: 03 May 2007
Posts: 695

PostPosted: Sun May 27, 2007 10:41 pm    Post subject: Reply with quote

Eureka !

Take the XY Wing that Keith identified - crucially by removing the 1 from r3c5 this reduces that square to a <46> bivalue.

Now we can eliminate that 6 that is troubling you:

ALS - Set A is r3c5 <46>.
Set B is r4c4 <67> and r6c5 <47>

Locked common is 4. The 6 in r1c4 can see both 6's in A & B and is thus eliminated.

NB these cells will also make up an XY chain - pincers at r3c5 and r4c4.
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Mogulmeister



Joined: 03 May 2007
Posts: 695

PostPosted: Sun May 27, 2007 11:10 pm    Post subject: Reply with quote

All this having been said there is a way to go to complete the puzzle.........
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Glassman



Joined: 21 Oct 2005
Posts: 50
Location: England

PostPosted: Sun May 27, 2007 11:33 pm    Post subject: Reply with quote

Keith I got side-tracked when I realised that your xy-wing eliminated the 1s at r2c1 and r2c3. That 57 was too tempting a prize not to be of use.

Mogulmeister I prefer yours as a simple xy-wing I struggle with ALSs.

Oh, and Keith, thank you for your diplomacy. However, has Andrew Stuart ever said that all his puzzles have a unique solution? ... or that he never makes a mistake? And, if so, would you believe him?

Glassman Cool
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Mogulmeister



Joined: 03 May 2007
Posts: 695

PostPosted: Sun May 27, 2007 11:47 pm    Post subject: Reply with quote

I put in the ALS because it got rid of your 6 but if x-y chain works as well so be it.

Personally, I would definitely always trust Andrew Stuart - he worked with and has now succeeded Michael Mepham(RIP) whose Sudoku puzzles always have one solution.

I think he does excellent work.
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