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Ad Hoc Puzzle 1

 
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Thu Dec 18, 2008 3:23 am    Post subject: Ad Hoc Puzzle 1 Reply with quote

I ran across this puzzle while experimenting with my puzzle generator. Anyone find it interesting?

Code:
 +-----------------------+
 | . . 1 | 9 7 . | 5 3 . |
 | . 7 . | . . 2 | . . . |
 | 9 . 4 | . . . | . . . |
 |-------+-------+-------|
 | 1 . . | 2 . 9 | 3 . . |
 | 8 . . | . 1 . | . 9 . |
 | . 9 . | 6 . 8 | 7 1 . |
 |-------+-------+-------|
 | 7 . . | 4 . 5 | . . . |
 | 4 . . | . 9 7 | . . 3 |
 | . . . | . . . | . 7 1 |
 +-----------------------+

Play this puzzle online at the Daily Sudoku site
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Marty R.



Joined: 12 Feb 2006
Posts: 5119
Location: Rochester, NY, USA

PostPosted: Thu Dec 18, 2008 6:21 am    Post subject: Reply with quote

Quote:
Anyone find it interesting?

Yes. And difficult. I was stuck after a couple of ERs and a Finned X-Wing and had to turn to my Medusa crutch. That opened things up just enough to finish it off with a Type 6 UR, a W-Wing and simple coloring. Took me over an hour.

(Be pretty embarrassing when someone reports their one-stepper).
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Thu Dec 18, 2008 8:17 am    Post subject: Reply with quote

Code:
.---------------------.---------------------.---------------------.
| 26     268    1     | 9      7      46    | 5      3      2468  |
| 356    7      3568  | 358    3468   2     | 1      468    9     |
| 9      23568  4     | 358    368    1     | 268    268    7     |
:---------------------+---------------------+---------------------:
| 1      456    7     | 2      45     9     | 3      468    4568  |
| 8      23456  2356  | 7      1      34    | 26     9      2456  |
| 235    9      235   | 6      345    8     | 7      1      245   |
:---------------------+---------------------+---------------------:
| 7      1      2368  | 4      2368   5     | 9      268    268   |
| 4      268    268   | 1      9      7     | 268    5      3     |
| 2356   23568  9     | 38     2368   36    | 4      7      1     |
'---------------------'---------------------'---------------------'

Quote:
I think its interesting because coloring takes it a long way.
1. coloring 4... r6c9 = r6c5 - r2c5 = r1c6; r1c9 <> 4
2. coloring 3... r3c2 = r9c2 - r7c3 = r7c5; r3c5 <> 3
3. coloring 8... r8c7 = r3c7 - r1c9 = r1c2; r8c2 <> 8
4. skyscraper 8... r1c2 = r9c2 - r9c4 = r2c4; r2c3 <> 8
5. coloring 6... r7c3 = r7c8 - r4c8 = r5c7; r5c3 <> 6
6. 45URr46c59[(8)r4c9 = (2)r6c9] - (2)r7c9 = (2)r7c8 - (2=8)r3c8; r4c8 <> 8
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tlanglet



Joined: 17 Oct 2007
Posts: 2461
Location: Northern California Foothills

PostPosted: Thu Dec 18, 2008 3:42 pm    Post subject: Reply with quote

Once again, I seemed to require more steps that others; a total of eight. Single digit techniques (coloring, kites, ER, skyscraper) worked, but I also got stuck until I finally found multi-coloring <8> that open everything up. I only used two two-digit steps: a Type 4 UR and a xy-wing.

Marty R. wrote:
Took me over an hour.

Don't feel bad Marty. I also required at least an hour.

Ted
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Thu Dec 18, 2008 3:57 pm    Post subject: Reply with quote

Code:
Techniques Used:  basics, 3x 2-String Kite, 3x Skyscraper, XY-Wing

I'm glad you (plural) found it interesting. However, since no one called it a fun puzzle, I will (try to) not post any more like this one. Thanks for the feedback!

[Edit: specifically identified which you.]


Last edited by daj95376 on Thu Dec 18, 2008 4:55 pm; edited 1 time in total
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tlanglet



Joined: 17 Oct 2007
Posts: 2461
Location: Northern California Foothills

PostPosted: Thu Dec 18, 2008 4:35 pm    Post subject: Reply with quote

daj95376 wrote:
Code:
Techniques Used:  basics, 3x 2-String Kite, 3x Skyscraper, XY-Wing

I'm glad you found it interesting. However, since no one called it a fun puzzle, I will (try to) not post any more like this one. Thanks for the feedback!

Danny, I did like the puzzle and thought it was a fun variation from puzzles with lots of bivalue cells. It was not something I would prefer as a steady diet but an occasional one would be great.

Ted
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Marty R.



Joined: 12 Feb 2006
Posts: 5119
Location: Rochester, NY, USA

PostPosted: Thu Dec 18, 2008 4:58 pm    Post subject: Reply with quote

Quote:
coloring 4... r6c9 = r6c5 - r2c5 = r1c6; r1c9 <> 4

Norm, could you explain how we get from r6c5 to r1c6? A kite emanating from box 5 makes the same elimination, but I still would like to understand your method. I can understand that if r6c9=4, then r6c5 doesn't and that's where I stop.
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Thu Dec 18, 2008 6:44 pm    Post subject: Reply with quote

I dont believe this its like a miraculous revelation. A couple of years ago I tried learning W-wings but couldnt understand the explanations complex arrays of big Gs and little gs, big Ws and little ws. I thought Id give it another shot today after progressing so far with this puzzle before getting stuck. I found this simple explanation from Keith.

http://www.dailysudoku.com/sudoku/forums/viewtopic.php?t=2008&sid=ca6ec00f3a2f9c52f1604e512708f40b

Now unless I am wrong, using a w wing, R1C2 cannot be a <2>. I used this method 3 times after this. Finished the thing in no time. Way, way easier than xy-wings.

Have I misunderstood? Seems far too elementary my Dear Watson!

Code:
            
+---------+-------+-------+   
| 26 28 . | . . . | . . . |   
| .  .  . | . . . | . . . |   
| .  .  . | . . . | . . . |   
+---------+-------+-------+   
| .  .  . | . . . | . . . |   
| .  .  . | . . . | . . . |   
| .  .  . | . . . | . . . |   
+---------+-------+-------+   
| .  .  . | . . . | . . . |   
| .  26 . | . . . | . . . |   
| .  .  . | . . . | . . . |
+---------+-------+-------+
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Thu Dec 18, 2008 7:40 pm    Post subject: Reply with quote

Marty R. wrote:
Quote:
coloring 4... r6c9 = r6c5 - r2c5 = r1c6; r1c9 <> 4

Norm, could you explain how we get from r6c5 to r1c6? A kite emanating from box 5 makes the same elimination, but I still would like to understand your method. I can understand that if r6c9=4, then r6c5 doesn't and that's where I stop.


Marty,
would it make more sense if I used the 4 in r2c8 in stead of the 4 in r1c6?

in other words, do you see the skyscraper easier in rows 2 and 6? on candidate 4?

the 4's in row 6 and the 4's in row 2 form a skyscraper which eliminate the 4 in r1c9 and r4c8. is that easier for you to see?
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Thu Dec 18, 2008 8:03 pm    Post subject: Reply with quote

Quote:
Now unless I am wrong, using a w wing, R1C2 cannot be a <2>.

Craig,
if you can show what makes either of the 2's in the (2,6) cells true, then I will tell you that you reached w-wing status.
but it seems to me like you missed explaining how the 6's are connected.


the classic w-wing involves 6 total candidates. your ending 2's and four 6's.
and looking at your diagram, you are missing two strongly linked 6's that reside outside the two (2,6) cells.

Code:
   6 = strong link = 6
   |                 |
(2=6)...............(6=2)


as you can see from the diagram, the strongly linked 6's each see one of the (2,6) cells.

this is the w-wing you are trying to form, can you show which 6's are strongly linked?
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Thu Dec 18, 2008 8:36 pm    Post subject: Reply with quote

Yeah thanks Norman - I thought it had to be harder than I thought (if you know what I mean). I missed out on the strong link thing. That would be like a Type 4 UR - I think. I'll work on it.

Cheers
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Marty R.



Joined: 12 Feb 2006
Posts: 5119
Location: Rochester, NY, USA

PostPosted: Thu Dec 18, 2008 10:33 pm    Post subject: Reply with quote

Quote:
Marty,
would it make more sense if I used the 4 in r2c8 in stead of the 4 in r1c6?

in other words, do you see the skyscraper easier in rows 2 and 6? on candidate 4?

the 4's in row 6 and the 4's in row 2 form a skyscraper which eliminate the 4 in r1c9 and r4c8. is that easier for you to see?


Norm, yes, the skyscraper is evident. I was unable to follow what I thought was a conventional coloring chain.

Thanks.
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