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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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 Posted: Wed Feb 15, 2012 7:59 pm Post subject: |
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| Quote: | | Not so easy for me, |
Nor me. Like getting from r2c7=6 to r5c8=6 or from r6c6=2 to r4c6=4. |
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arkietech
Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA
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| Posted: Wed Feb 15, 2012 8:16 pm Post subject: |
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| Luke451 wrote: | | SudoQ wrote: | | moshero3 wrote: | | does anyone has a simpler solution to this one? |
| Code: | r1c5 or r3c6 = 6
r1c5=6 -> r2c7=6, r5c8=6, r4c8=4 -> r4c4<4> r7c6=5, r6c8=5, r6c6=2, r4c6=4 -> r4c4<>4 |
I don't know if this is a simple solution,
but I think it's easy to understand.
/SudoQ |
Not so easy for me, |
Works for me  SudoQ, How did you pick r1c5 or r3c6 = 6?  |
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Luke451
Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California
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| Posted: Wed Feb 15, 2012 9:17 pm Post subject: |
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| Hmm, I see ...it's like a net. SudoQ's first chain "remembers" -6r5c5, the second "remembers" -6r4c6. The notation's just a tad sparse, perhaps. |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Wed Feb 15, 2012 11:02 pm Post subject: |
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| Luke451 wrote: | Not so easy for me, SudoQ. I can't get either chain to work starting from the position after basics.
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Luke451,
SudoQ uses networks -- not chains. |
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SudoQ
Joined: 02 Aug 2011
Posts: 127
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| Posted: Wed Feb 15, 2012 11:31 pm Post subject: |
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| Luke451 wrote: | | Hmm, I see ...it's like a net. SudoQ's first chain "remembers" -6r5c5, the second "remembers" -6r4c6. The notation's just a tad sparse, perhaps. |
Sorry, I skipped the pencilmarks.
| Code: |
r1c5=6 -> r1c79<>6 -> r2c7=6 -> r5c7<>6 ->
-> r5c5<>6 -> r5c8<>4(=6) -> r4c8=4 -> r4c4<>4
r3c6=6 -> r7c6=5 -> r7c9<>5 -> r6c8<>2(=5) -> r6c6=2 -> r4c6<>2 ->
-> r4c6<>6 -> r4c6=4 -> r4c4<>4
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/SudoQ |
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SudoQ
Joined: 02 Aug 2011
Posts: 127
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| Posted: Wed Feb 15, 2012 11:37 pm Post subject: |
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| arkietech wrote: | | How did you pick r1c5 or r3c6 = 6? |
I must admit that my solver program helped me. 
/SudoQ |
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Luke451
Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California
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| Posted: Thu Feb 16, 2012 5:49 am Post subject: |
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| moshero3 wrote: | | does anyone has a simpler solution to this one? |
That’s what we’re all after, isn’t it? 
This puzzle is rated SE 7.3 at the basics stage. Once you get over about SE 7.0, something more advanced is probably needed. That’s why no one can offer you one common wing or pattern to take it down.
Personally I’d go with an AIC, but I can’t find one as efficient or clever as that posted above by JC Van Hay. |
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moshero3
Joined: 11 Feb 2012
Posts: 12
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| Posted: Thu Feb 16, 2012 6:59 am Post subject: how do you get the intuition to do that |
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hi all,
What was the intuition to chose those cells & digits:
r1c5 or r3c6 = 6
r4c4<>4
how did you spot that? |
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SudoQ
Joined: 02 Aug 2011
Posts: 127
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| Posted: Thu Feb 16, 2012 10:26 am Post subject: Re: how do you get the intuition to do that |
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| moshero3 wrote: |
What was the intuition to chose those cells & digits:
r1c5 or r3c6 = 6
r4c4<>4
how did you spot that? |
In this puzzle, there are initially 70 'bi-cells, where 62 of these (= 89%) can eliminate candidates.
I don't know how to find the most effective ones without 'trial and error'.
An example of a shorter first step is:
| Code: | r3c4=1/8
r3c4=1 -> r9c5<>6
r3c4=8 -> r5c4=3 -> r8c4=6 -> r9c5<>6 |
(After this you can show that r5c5<>8.)
/SudoQ |
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SudoQ
Joined: 02 Aug 2011
Posts: 127
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| Posted: Fri Feb 17, 2012 11:12 am Post subject: |
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| moshero3 wrote: | | does anyone has a simpler solution to this one? |
When I looked into this, it turns out that you can show that r5c5<>8 right after basics.
It takes fewer steps to do so than with other solutions.
The question is whether it can be considered to be 'simpler'?
| Code: | r5c5=8 -> r5c7<>8 ->
-> r5c1=2 -> r5c7=6 -> r1c9=6
-> r6c4=3 -> r8c4=6 -> r1c5=6 -> r1-err |
/SudoQ |
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Luke451
Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California
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| Posted: Fri Feb 17, 2012 4:20 pm Post subject: |
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| SudoQ wrote: | | moshero3 wrote: | | does anyone has a simpler solution to this one? |
When I looked into this, it turns out that you can show that r5c5<8> r5c7<8>
-> r5c1=2 -> r5c7=6 -> r1c9=6
-> r6c4=3 -> r8c4=6 -> r1c5=6 -> r1-err[/code]/SudoQ |
Simple, yes, but this technique has a history of controversy.
Arbitrarily plugging a value into a cell and setting off to find contradictions is considered by some in the solving community as unnecessarily assumptive, with elements of trial and error, especially when more "elegant" approaches are available.
Others find the practice a perfectly acceptable and irrefutably logical way to bring down any puzzle.
I've seen good arguments from both sides, and in the end, it's a personal choice. |
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