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Mepham, May 6

 
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Marty R.



Joined: 12 Feb 2006
Posts: 5063
Location: Rochester, NY, USA

PostPosted: Sun Jun 17, 2007 3:35 pm    Post subject: Mepham, May 6 Reply with quote

I'm sick of staring at it and I'm not ready for chains yet.

Code:

+--------+------------+-----------+
| 7 24 5 | 39  6  29  | 13 149 8  |
| 1 24 8 | 379 5  279 | 6  49  34 |
| 3 9  6 | 4   8  1   | 5  2   7  |
+--------+------------+-----------+
| 2 3  4 | 6   9  5   | 7  8   1  |
| 6 7  9 | 18  14 48  | 23 5   23 |
| 8 5  1 | 2   7  3   | 4  6   9  |
+--------+------------+-----------+
| 9 1  7 | 5   24 6   | 8  3   24 |
| 5 8  2 | 17  3  47  | 9  14  6  |
| 4 6  3 | 89  12 89  | 12 7   5  |
+--------+------------+-----------+

Play this puzzle online at the Daily Sudoku site
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Steve R



Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England

PostPosted: Sun Jun 17, 2007 6:58 pm    Post subject: Reply with quote

Marty

Iíve looked at this far too long to be sure I have it right but I think you can finish in two steps.

First eliminate 4 from r1c8 using the ALSs A = {r8c4, r8c8} and B = {r2c4, r2c8, r2c9} with the restricted common candidate 7. This gives

Code:
+--------+------------+-----------+
| 7 4  5 | 39  6  29  | 13 19  8  |
| 1 2  8 | 379 5  79  | 6  49  34 |
| 3 9  6 | 4   8  1   | 5  2   7  |
+--------+------------+-----------+
| 2 3  4 | 6   9  5   | 7  8   1  |
| 6 7  9 | 18  14 48  | 23 5   23 |
| 8 5  1 | 2   7  3   | 4  6   9  |
+--------+------------+-----------+
| 9 1  7 | 5   24 6   | 8  3   24 |
| 5 8  2 | 17  3  47  | 9  14  6  |
| 4 6  3 | 89  12 89  | 12 7   5  |
+--------+------------+-----------+

If you are prepared to assume uniqueness, 9 can then be placed in r2c4; if not, another ALS argument does the trick.

I could not find a solution which avoided both chains and ALSs.

Steve


Last edited by Steve R on Sun Jun 17, 2007 8:13 pm; edited 1 time in total
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Marty R.



Joined: 12 Feb 2006
Posts: 5063
Location: Rochester, NY, USA

PostPosted: Sun Jun 17, 2007 8:00 pm    Post subject: Reply with quote

Steve, thank you. My next ALS will be my first. I did look unsuccessfully for them for a few minutes, but I really don't know how to look for them.

Quote:
If you are prepared to assume uniqueness, 9 can then be placed in r3c4; if not, another ALS argument does the trick.


R3c4 is probably a typo, perhaps you meant r2c4, since that is a BUG+1 after the triple in row 1 solves r1c6. To me, the concept of uniqueness is synonymous with URs, but I can see where it's also involved with BUGs as well.

Again, thanks.
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Steve R



Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England

PostPosted: Sun Jun 17, 2007 8:14 pm    Post subject: Reply with quote

Yes, it was a typo, now corrected, than you.

Steve
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Mogulmeister



Joined: 03 May 2007
Posts: 695

PostPosted: Mon Jun 18, 2007 3:06 pm    Post subject: Reply with quote

Easiest early technique I could see was deploying an XY chain removing 1 from r5c5 pincers on 1's at r5c4 & r9c5 - but since you didn't want chains I needed multiple ALS to do it. Nice puzzle.
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Marty R.



Joined: 12 Feb 2006
Posts: 5063
Location: Rochester, NY, USA

PostPosted: Mon Jun 18, 2007 3:52 pm    Post subject: Reply with quote

Quote:
Easiest early technique I could see was deploying an XY chain removing 1 from r5c5 pincers on 1's at r5c4 & r9c5 - but since you didn't want chains


MM,

XY Chains are acceptable; it's the other chains that are more guesswork that don't satisfy me. However, unfortunately, I'm not seeing the chain that uses those pincers to remove that 1 from r5c5.
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Mogulmeister



Joined: 03 May 2007
Posts: 695

PostPosted: Mon Jun 18, 2007 8:35 pm    Post subject: Reply with quote

Marty,

You know me - a picture is worth a thousand words etc..


Pincers in green, steps in lilac, eliminated in orange.

Hope this displays it:

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Mogulmeister



Joined: 03 May 2007
Posts: 695

PostPosted: Mon Jun 18, 2007 9:07 pm    Post subject: Reply with quote

Needless to say you won't be too surprised that an equally telling neighbouring elimination can also be made on the 8's:

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Marty R.



Joined: 12 Feb 2006
Posts: 5063
Location: Rochester, NY, USA

PostPosted: Tue Jun 19, 2007 4:47 am    Post subject: Reply with quote

MM, thank you.
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Myth Jellies



Joined: 27 Jun 2006
Posts: 64

PostPosted: Thu Jun 21, 2007 7:53 am    Post subject: Re: Mepham, May 6 Reply with quote

Code:

+--------+-------------+------------+
| 7 24 5 | 39   6  29  | 13 19+4 8  |
| 1 24 8 | 37+9 5  27+9| 6  49   34 |
| 3 9  6 | 4    8  1   | 5  2    7  |
+--------+-------------+------------+
| 2 3  4 | 6    9  5   | 7  8    1  |
| 6 7  9 | 18   14 48  | 23 5    23 |
| 8 5  1 | 2    7  3   | 4  6    9  |
+--------+-------------+------------+
| 9 1  7 | 5    24 6   | 8  3    24 |
| 5 8  2 | 17   3  47  | 9  14   6  |
| 4 6  3 | 89   12 89  | 12 7    5  |
+--------+-------------+------------+

How about a BUG+3 grid....At least one of the candidates after the + must be true....Pretty obvious via the 49-cell in r2c8 that r2c9 <> 4
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Mogulmeister



Joined: 03 May 2007
Posts: 695

PostPosted: Thu Jun 21, 2007 8:00 am    Post subject: Reply with quote

Thanks Myth,

I must confess I tend to overlook BUG (only ever used it once before).
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Steve R



Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England

PostPosted: Thu Jun 21, 2007 11:24 am    Post subject: Reply with quote

Is it a BUG+3?

Code:
+--------+-------------+------------+
| 7 24 5 | 39   6  29  | 13 19+4 8  |
| 1 24 8 | 37+9 5  27+9| 6  49   34 |
| 3 9  6 | 4    8  1   | 5  2    7  |
+--------+-------------+------------+
| 2 3  4 | 6    9  5   | 7  8    1  |
| 6 7  9 | 18   14 48  | 23 5    23 |
| 8 5  1 | 2    7  3   | 4  6    9  |
+--------+-------------+------------+
| 9 1  7 | 5    24 6   | 8  3    24 |
| 5 8  2 | 17   3  47  | 9  14   6  |
| 4 6  3 | 89   12 89  | 12 7    5  |
+--------+-------------+------------+

I thought a BUG+ meant that, if the candidates after the + sign were omitted, the remaining candidates occurred twice in each house. Here three 9s would be left in the first row.

What have I missed?

Steve
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Mogulmeister



Joined: 03 May 2007
Posts: 695

PostPosted: Thu Jun 21, 2007 11:35 am    Post subject: Reply with quote

If you omitted the +9's in r2 this would de facto make r2c8 a 9 and eliminate the 9 in r1c8 thereby creating the deadly pattern.

Therefore one of the 9's in box two must be true if we are to demonstrate uniqueness.

(Forgive me I'm not a BUG specialist) Embarassed
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Steve R



Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England

PostPosted: Thu Jun 21, 2007 11:57 am    Post subject: Reply with quote

Yes, that's it. Thank you.

Steve
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Myth Jellies



Joined: 27 Jun 2006
Posts: 64

PostPosted: Thu Jun 21, 2007 4:53 pm    Post subject: Reply with quote

My mistake, it is not a BUG+3; at least not the way I showed it. I guess I have forgotten how to count to two. As Mogulmeister showed, there is something there, but my logic was faulty. Embarassed
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Myth Jellies



Joined: 27 Jun 2006
Posts: 64

PostPosted: Thu Jun 21, 2007 5:26 pm    Post subject: Re: Mepham, May 6 Reply with quote

Code:

+--------+-------------+------------+
| 7 24 5 | 39   6  29  | 13 14+9 8  |
| 1 24 8 | 37+9 5  27+9| 6  9+4  34 |
| 3 9  6 | 4    8  1   | 5  2    7  |
+--------+-------------+------------+
| 2 3  4 | 6    9  5   | 7  8    1  |
| 6 7  9 | 18   14 48  | 23 5    23 |
| 8 5  1 | 2    7  3   | 4  6    9  |
+--------+-------------+------------+
| 9 1  7 | 5    24 6   | 8  3    24 |
| 5 8  2 | 17   3  47  | 9  14   6  |
| 4 6  3 | 89   12 89  | 12 7    5  |
+--------+-------------+------------+

I think this is the real BUG avoidance grid (BUG+4), which is a little more complex than usual because of the implied single in r2c8. Note that all of the plus candidates force r2c8 = 4. I think the implied single really means that you have a BUG-Lite.

I think the BUG-Lite way of looking at it is that all of the unsolved candidates before the plus in the cell (if one exists) in every cell except r2c8 forms a gigantic BUG-Lite+3 and all those + digits are nines! With 23 out of 24 unsolved cells forming a BUG-Lite, it is one of the biggest ever noted.

Code:

+--------+-------------+------------+
| 7 24 5 | 39   6  29  | 13 14+9 8  |
| 1 24 8 | 37+9 5  27+9| 6 *49   34 |
| 3 9  6 | 4    8  1   | 5  2    7  |
+--------+-------------+------------+
| 2 3  4 | 6    9  5   | 7  8    1  |
| 6 7  9 | 18   14 48  | 23 5    23 |
| 8 5  1 | 2    7  3   | 4  6    9  |
+--------+-------------+------------+
| 9 1  7 | 5    24 6   | 8  3    24 |
| 5 8  2 | 17   3  47  | 9  14   6  |
| 4 6  3 | 89   12 89  | 12 7    5  |
+--------+-------------+------------+

In this case the 23 unstarred unsolved cells form a BUG-Lite+3.
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Steve R



Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England

PostPosted: Thu Jun 21, 2007 5:35 pm    Post subject: Reply with quote

I only spotted the ALS in the first place by bumbling around the extended uniqueness pattern in r12c268. To do that without seeing the elimination puts me squarely in the doghouse too. Good thing thereís no thread for the greatest number fumbling a fairly straightforward puzzle.

Is it the sun? Is it the wine? Or is it the boogie?

Steve
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Mogulmeister



Joined: 03 May 2007
Posts: 695

PostPosted: Thu Jun 21, 2007 8:26 pm    Post subject: Reply with quote

Arrow All of the above. Smile
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