Rambling

Everything about Sudoku that doesn't fit in one of the other sections

Postby daj95376 » Fri Aug 01, 2008 4:35 pm

ttt wrote:I present your elimination r8c9=4 by using dual Kraken - 3's on row 3 and cell r1c7 :

I can barely follow basic Eureka notation. Your original chains were at my limit for understanding. Sorry!
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Postby daj95376 » Sat Aug 16, 2008 10:02 pm

My solver finds: Singles, a short Chain, and Singles. Does it have a more zippy solution?

Code: Select all
 +-----------------------+
 | 5 4 . | . 6 . | . . 3 |
 | 2 . . | . . 9 | . . . |
 | . . 9 | 4 5 . | . . 2 |
 |-------+-------+-------|
 | . . 6 | 9 . 3 | . . 1 |
 | 1 . 4 | . . 7 | 9 . . |
 | . 2 . | 1 4 5 | . . . |
 |-------+-------+-------|
 | . . . | . 1 . | . . . |
 | . . . | . . . | . 7 . |
 | 4 . 5 | 7 . . | . . 9 |
 +-----------------------+
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Postby hobiwan » Sun Aug 17, 2008 12:00 pm

daj95376 wrote:My solver finds: Singles, a short Chain, and Singles. Does it have a more zippy solution?

My solver finds a few ALS to replace the chain, but nothing special. One possibility:

Code: Select all
Singles
Almost Locked Set XZ-Rule: A=r4c125 - {2578}, B=r5c59 - {258}, X=2, Z=5 => r4c78,r5c2<>5
Singles
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Postby daj95376 » Sun Aug 17, 2008 12:55 pm

hobiwan wrote:
daj95376 wrote:My solver finds: Singles, a short Chain, and Singles. Does it have a more zippy solution?

My solver finds a few ALS to replace the chain, but nothing special. One possibility:

Code: Select all
Singles
Almost Locked Set XZ-Rule: A=r4c125 - {2578}, B=r5c59 - {258}, X=2, Z=5 => r4c78,r5c2<>5
Singles

Thanks for checking hobiwan! FWIW: your ALS produces the same eliminations as my short chain. Since there are plenty of backdoor singles to crack this PM, maybe there's an obscure UR/DP present as well. Heck, there may even be a Kraken fish -- something I forgot to check.
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Postby ttt » Mon Aug 18, 2008 4:06 am

Hi Daj,
My solutions :

1) [r4c2]=5=[r5c2]-5-[r5c9]-8-[r5c5]=8=[r4c5]-8-[r4c1]-7-[r4c2] => r4c2<>7, singles
2) [r6c3]-8-[r4c1]-7=[r4c2]=7=[r3c2]-7- ALS:([r12c3]=1|8=[r12c3])-8-[r6c3] => r6c3<>8, singles
3) [r6c3]-8-[r4c1]-7-[r7c1]=7=[r7c3](-3-[r7c3])=2=[r8c3](-3-[r8c3])-3-[r6c3] => r6c3<>8, singles

I’m not sure for presenting my solutions 2 & 3, I’m new for NL notation...:D

BTW, thanks to you and Ronk for helping me to learn NL notation.

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Postby daj95376 » Tue Sep 02, 2008 7:04 pm

I must admit that I've deliberately avoided learning ALS. Some things make my head go TILT.

http://forum.enjoysudoku.com/viewtopic.php?p=60713#p60713

999_Springs wrote:Then I found an ALS xz
ALS A=r7c46r8c5r9c6
ALS B=r456c5r5c6
x=1 z=7 r8c6<>7
(It's not that necessary but I hardly ever find these things, so I might as well use it...)

Code: Select all
 +--------------------------------------------------------------------------------+
 |  69      5       2       |  4       8       1       |  79      3679    367     |
 |  4689    346     348     |  69      7       569     |  1       24569   24568   |
 |  4689    17      17      |  3       2       569     |  4589    4569    4568    |
 |--------------------------+--------------------------+--------------------------|
 |  456     1467    1457    |  8      B1469    2       |  4579    134579  13457   |
 |  3       124     1458    |  179    B149    B479     |  6       12459   12458   |
 |  2468    9       1478    |  5      B146     3       |  2478    1247    12478   |
 |--------------------------+--------------------------+--------------------------|
 |  1       248     6       | A79      3      A4789    |  2457    2457    2457    |
 |  245     234     345     |  167    A14      46-7    |  2347    8       9       |
 |  7       348     9       |  2       5      A48      |  34      16      16      |
 +--------------------------------------------------------------------------------+
 # 136 eliminations remain

If we start with:            [r8c6]-7-[r5c6]
There is a strong link on 7: [r5c6]=7=[r5c4]
There is a strong link on 1: [r5c4]=1=[r8c4]
There is a strong link on 6: [r8c4]=6=[r8c6]

Four cells and four links. That I can understand.
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Postby 999_Springs » Wed Sep 03, 2008 3:20 pm

I don't look for these ALSs on purpose. I still have a lot of trouble finding them. That one basically just came out at me for no reason at all. I will now say that this is only the second ALS elimination I have ever found.

There might be a simpler ALS elimination for all I know. (If there is then I can't find it.)

I was never able to find ALSs effectively. I will add a link to show that when I have the time.
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Postby daj95376 » Wed Sep 03, 2008 3:39 pm

999_Springs wrote:I was never able to find ALSs effectively. I will add a link to show that when I have the time.

I was not criticizing you or your post. I find ALS eliminations to be foreign when compared to chains that often perform the same eliminations. Your ALS was just a convenient example.
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Postby daj95376 » Wed Sep 17, 2008 12:34 am

Is there a name for a pattern where identical XY cells are pincers in a (possibly grouped) chain of >4 cells linked by X such that either end must be true for Y

Code: Select all
9-[r6c1]-3-[r3c1]=3=[r3c5]-3-[r12c4]=3=[r8c4]-3-[r8c2]-9
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Postby tarek » Wed Sep 17, 2008 3:13 am

because W seems to be the trend now ...

How about a W-chain:D ?

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Postby daj95376 » Wed Sep 17, 2008 5:43 am

Ahhhhhh, thanks tarek for reminding me of ronk's suggestion awhile back. My memory is swiss cheese anymore:!:

I also found a 2007 entry in the Daily Sudoku Forum where keith calls it a General Remote Pair.

I like both designations.
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Postby ttt » Wed Sep 17, 2008 10:12 am

Hi Danny,
I don’t know why, but I like you… Perhaps, because of WE like SUDOKU…

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Postby Draco » Thu Sep 18, 2008 12:46 pm

daj95376 wrote:
hobiwan wrote:
daj95376 wrote:My solver finds: Singles, a short Chain, and Singles. Does it have a more zippy solution?

My solver finds a few ALS to replace the chain, but nothing special. One possibility:

Code: Select all
Singles
Almost Locked Set XZ-Rule: A=r4c125 - {2578}, B=r5c59 - {258}, X=2, Z=5 => r4c78,r5c2<>5
Singles

Thanks for checking hobiwan! FWIW: your ALS produces the same eliminations as my short chain. Since there are plenty of backdoor singles to crack this PM, maybe there's an obscure UR/DP present as well. Heck, there may even be a Kraken fish -- something I forgot to check.

Weighing in waaay late... another simple forcing chain that cracks the puzzle (after the initial Singles pass):
Code: Select all
r5c2=3 r6c3=8 + r5c8=3 r5c5=2 r4c5=8 ==> r4c1<>8

Cheers...

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Postby daj95376 » Thu Sep 18, 2008 3:59 pm

ttt wrote:Hi Danny,
I don’t know why, but I like you… Perhaps, because of WE like SUDOKU…

Thanks ttt, it's always nice to be liked:!:

I'm just sorry that I only understand some of the replies you took time to post. Maybe some day, I'll understand Eureka! notation better.

I may often be difficult, but I like you and many other members of this forum as well.
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Postby daj95376 » Thu Sep 18, 2008 4:20 pm

Draco wrote:Weighing in waaay late... another simple forcing chain that cracks the puzzle (after the initial Singles pass):
Code: Select all
r5c2=3 r6c3=8 + r5c8=3 r5c5=2 r4c5=8 ==> r4c1<>8

Cheers...

Hello Draco,

Yes, your forcing chain does the job very nicely. Did you consider converting it into:

Code: Select all
8-[r6c3]-3-[r5c2]=3=[r5c8]=2=[r5c5]-2-[r4c5]-8 => [r4c12]<>8

To me, the above AIC chain is a forcing chain based on the bivalue candidates in [r6c3] -- or the bivalue candidates in [r4c5].
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