The New Sudoku Players' Forum

by **ArkieTech** » Tue Jan 23, 2018 12:11 pm

Code: Select all: *-----------* |94.|.58|.2.| |...|6..|...| |..1|..4|9.5| |---+---+---| |...|..7|..1| |.6.|.9.|.7.| |3..|1..|...| |---+---+---| |2.7|5..|4..| |...|..2|...| |.5.|84.|.92| *-----------*

Play/Print this puzzle online

by **200e200w** » Tue Jan 23, 2018 3:03 pm

Code: Select all: .---------------------.---------------------.---------------------. | 9 4 6 | 37 5 8 | 1 2 7-3 | | 57 23 25 | 6 1 9 | a38 g348 h47-3 | | 78 38 1 | 237 23 4 | 9 6 5 | :---------------------+---------------------+---------------------: | 458 28 9 | 234 2368 7 | 2568-3 3458 1 | | 1 6 c2458 | 234 9 35 | b258-3 7 i34 | | 3 7 e2458 | 1 268 56 | 2568 f458 9 | :---------------------+---------------------+---------------------: | 2 9 7 | 5 36 36 | 4 1 8 | | 48 1 d48 | 9 7 2 | 35 35 6 | | 6 5 3 | 8 4 1 | 7 9 2 | '---------------------'---------------------'---------------------'

(3=8)r2c7 - r5c7 = r5c3 - (8=4)r8c3 - r6c3 = r6c8 - r2c8 = r2c9 - (4=3)r5c9 => -3 r12c9,r45c7; stte

200e200w

by **Cenoman** » Tue Jan 23, 2018 5:19 pm

Code: Select all: +--------------------+--------------------+-----------------------+ | 9 4 6 | 37 5 8 | 1 2 37 | | 57 23 25 | 6 1 9 | b38 a38-4 i347 | | 78 38 1 | 237 23 4 | 9 6 5 | +--------------------+--------------------+-----------------------+ | 458 28 9 | 234 2368 7 | 23568 3458 1 | | 1 6 d2458 | 234 9 35 | c2358 7 h34 | | 3 7 f2458 | 1 268 56 | 2568 g458 9 | +--------------------+--------------------+-----------------------+ | 2 9 7 | 5 36 36 | 4 1 8 | | 48 1 e48 | 9 7 2 | 35 35 6 | | 6 5 3 | 8 4 1 | 7 9 2 | +--------------------+--------------------+-----------------------+

(8)r2c8 = r2c7 - r5c7 = r5c3 - (8=4)r8c3 - r6c3 = r6c8 - r5c9 = (4)r2c9 => -4 r2c8; stte

by **SteveG48** » Tue Jan 23, 2018 7:34 pm

Code: Select all: *--------------------------------------------------------------------* | 9 4 6 | 37 5 8 | 1 2 37 | |c57 b23 b25 | 6 1 9 |a38 a348 347 | | 78 38 1 | 237 23 4 | 9 6 5 | *----------------------+----------------------+----------------------| |d458 cd28 9 | 234 2368 7 | 23568 e3458 1 | | 1 6 2458 | 234 9 35 | 2358 7 e34 | | 3 7 2458 | 1 268 56 | 2568 58-4 9 | *----------------------+----------------------+----------------------| | 2 9 7 | 5 36 36 | 4 1 8 | | 48 1 48 | 9 7 2 | 35 35 6 | | 6 5 3 | 8 4 1 | 7 9 2 | *--------------------------------------------------------------------*

(4=3)r2c78 - (3=25)r2c23 - (5|2)r2c1,r4c2 = (58)r4c12 - (5|8=4)b6p26 => -4 r6c8 ; stte

by **Leren** » Tue Jan 23, 2018 7:52 pm

Code: Select all: *----------------------------------------------* | 9 4 6 | 37 5 8 | 1 2 7-3 | | 57 23 25 | 6 1 9 |a38 348 47-3 | | 78 38 1 | 237 23 4 | 9 6 5 | |-------------+-------------+------------------| | 458 28 9 | 234 2368 7 | 2568-3 3458 1 | | 1 6 c2458 | 234 9 35 |b258-3 7 d34 | | 3 7 e2458 | 1 268 56 | 2568 f458 9 | |-------------+-------------+------------------| | 2 9 7 | 5 36 36 | 4 1 8 | | 48 1 d48 | 9 7 2 | 35 35 6 | | 6 5 3 | 8 4 1 | 7 9 2 | *----------------------------------------------*

A bit shorter than the first solution :

(3=8) r2c7 - r5c7 = r5c3 - (8=4) r8c3 - r6c3 = r6c8 - (4=3) r5c9 => - 3 r12c9, r45c7; stte

Leren

by **Sudtyro2** » Tue Jan 23, 2018 8:43 pm

Code: Select all: +-----------------+---------------+------------------+ | 9 4 6 | 37 5 8 | 1 2 37 | | c57 c23 c25 | 6 1 9 | c38 c348 347 | | d78 38 1 | 237 23 4 | 9 6 5 | +-----------------+---------------+------------------+ | 58-4 28 9 | 234 2368 7 | 23568 3458 1 | | 1 6 2458 | 234 9 35 | 2358 7 34 | | 3 7 a2458 | 1 268 56 | 2568 b458 9 | +-----------------+---------------+------------------+ | 2 9 7 | 5 36 36 | 4 1 8 | | d48 1 8-4 | 9 7 2 | 35 35 6 | | 6 5 3 | 8 4 1 | 7 9 2 | +-----------------+---------------+------------------+

4r6c3 = r6c8 - (4=23587)r2c12367 - (7=84)r38c1 => -4r8c3,r4c1; stte.

SteveC

by **200e200w** » Tue Jan 23, 2018 10:07 pm

Hi Leren,

(3=8) r2c7 - r5c7 = r5c3 - (8=4) r8c3 - r6c3 = r6c8 - (4=3) r5c9 => - 3 r12c9, r45c7; stte

I didn't see the weak link (4)r6c8 - r5c9. That's why my chain is so long and not as elegant as yours. I'll try to improve it in later puzzles.

200e200w

by **200e200w** » Tue Jan 23, 2018 10:27 pm

Hi Steve,

(4=3)r2c78 - (3=25)r2c23 - (5|2)r2c1,r4c2 = (58)r4c12 - (5|8=4)b6p26 => -4 r6c8 ; stte

Your chain (or in reality Net) should be written as:

Code: Select all: (4=38)r2c78 - (3=25)r2c23 - (5)r2c1 = r4c1 - r4c8 \ \\ (2=8)r4c2 - r4c8 ===== (34)b6p26 => -4 r6c8; stte

200e200w

by **Marty R.** » Tue Jan 23, 2018 10:59 pm

Code: Select all: ┌───────────────────────┬───────────────────────┬───────────────────────┐ │ 9 4 6 │ 37 5 8 │ 1 2 37 │ │ │ │ │ │ 57 23 25 │ 6 1 9 │ 38 348 347 │ │ │ │ │ │ 78 38 1 │ 237 23 4 │ 9 6 5 │ ├───────────────────────┼───────────────────────┼───────────────────────┤ │ 458 28 9 │ 234 2368 7 │ 23568 3458 1 │ │ │ │ │ │ 1 6 2458 │ 234 9 35 │ 2358 7 34 │ │ │ │ │ │ 3 7 2458 │ 1 268 56 │ 2568 458 9 │ ├───────────────────────┼───────────────────────┼───────────────────────┤ │ 2 9 7 │ 5 36 36 │ 4 1 8 │ │ │ │ │ │ 48 1 48 │ 9 7 2 │ 35 35 6 │ │ │ │ │ │ 6 5 3 │ 8 4 1 │ 7 9 2 │ └───────────────────────┴───────────────────────┴───────────────────────┘

Kite (4) hinged b6
4r2c9=r6c3
4r2c9-(4=3)r5c9
4r6c3-(4=358)r268c8-(358=4)r2684c8-(4=3)r5c9=> 3r5c9

by **200e200w** » Tue Jan 23, 2018 11:12 pm

Hi Marty R.,

Kite (4) hinged b6
4r2c9=r6c3
4r2c9-(4=3)r5c9
4r6c3-(4=358)r268c8-(358=4)r2684c8-(4=3)r5c9=> 3r5c9

According to how the candidates for 4 are placed in c8, your chain is incorrect, because (4)r6c3 - (4=358)r268c8 is incorrect. You cannot prove that r5c9=3 using these chains. The correct chain could be:

Code: Select all: (4)r6c3 - r6c8 =====================================\ \ \\ (4=8)r8c3 - r5c3 = r5c7 - r2c7 = (8-4)r2c8 = r4c8 - (4=3)r5c9

200e200w

by **Marty R.** » Wed Jan 24, 2018 12:23 am

200e200w wrote:Hi Marty R.,
Kite (4) hinged b6
4r2c9=r6c3
4r2c9-(4=3)r5c9
4r6c3-(4=358)r268c8-(358=4)r2684c8-(4=3)r5c9=> 3r5c9

According to how the candidates for 4 are placed in c8, your chain is incorrect, because (4)r6c3 - (4=358)r268c8 is incorrect. You cannot prove that r5c9=3 using these chains. The correct chain could be:
Code: Select all
(4)r6c3 - r6c8 (=====================================\) (\) (\\) (4=8)r8c3 - r5c3 = r5c7 - r2c7 = (8-4)r2c8 = r4c8 - (4=3)r5c9

200e200w

OK, I agree. I was doing the puzzle off an incorrect grid, in which r2c8 was 38 rather than 348. I don't understand the portion of your notation that I've enclosed in ().

by **pjb** » Wed Jan 24, 2018 6:42 am

Code: Select all: 9 4 6 | 37 5 8 | 1 2 37 57 23 25 | 6 1 9 |ag38 g348 347 78 38 1 | 237 23 4 | 9 6 5 ------------------------+----------------------+--------------------- 458 28 9 | 234 2368 7 | 23568 3458 1 1 6 c2458 | 234 9 35 |b2358 7 34 3 7 e2458 | 1 268 56 | 2568 f458 9 ------------------------+----------------------+--------------------- 2 9 7 | 5 36 36 | 4 1 8 48 1 d48 | 9 7 2 | 35 35 6 6 5 3 | 8 4 1 | 7 9 2

(3=8)r2c7 - r5c7 = r5c3 - (8=4)r8c3 - r6c3 = r6c8 - (38)r2c78 => -3r12c9, r2c2; stte

Phil

by **200e200w** » Wed Jan 24, 2018 7:27 am

Hi Phil,

(3=8)r2c7 - r5c7 = r5c3 - (8=4)r8c3 - r6c3 = r6c8 - (38)r2c78 => -3r12c9, r2c2; stte

Should be:
(3=8)r2c7 - r5c7 = r5c3 - (8=4)r8c3 - r6c3 = r6c8 - (4=38)r2c78 => -3r12c9, r2c2; stte

200e200w

by **SteveG48** » Wed Jan 24, 2018 2:43 pm

200e200w wrote:Hi Steve,
(4=3)r2c78 - (3=25)r2c23 - (5|2)r2c1,r4c2 = (58)r4c12 - (5|8=4)b6p26 => -4 r6c8 ; stte

Your chain (or in reality Net) should be written as:
Code: Select all
(4=38)r2c78 - (3=25)r2c23 - (5)r2c1 = r4c1 - r4c8 \ \\ (2=8)r4c2 - r4c8 ===== (34)b6p26 => -4 r6c8; stte

200e200w

Hi, 200e200w. Thanks for reading and for the comment.

I certainly agree that my chain can be written as you've indicated, but I don't agree that it should be, and I don't see why you would want to.

As I've written it, the chain is a bi-directional AIC and follows that rules posted by David P. Bird:

"Nevertheless for an alternating inference chain to be bi-directional the same basic rules must always be followed.
1) Each term in the chain must be a Boolean which will be interpreted as either being true or false
2) The link types must alternate between weak and strong
3) Each link must be stand-alone and independent of the truth states of candidates elsewhere in the chain."

To me, rule 3 is the thing that distinguishes between a net solution and a non-net solution. As a matter of personal preference, I always try to present a solution as a bi-directional AIC if I can, provided that the notation doesn't get ridiculously complex. I admit to not always being successful on either count.

by **200e200w** » Wed Jan 24, 2018 3:47 pm

Hi Steve,

As I've written it, the chain is a bi-directional AIC...

For me, it isn't a bi-directional AIC. I also think that it doesn't follow the rule 3:

3) Each link must be stand-alone and independent of the truth states of candidates elsewhere in the chain."

That's my opinion.

200e200w

The New Sudoku Players' Forum

January 23, 2018

January 23, 2018

Re: January 23, 2018

Re: January 23, 2018

Re: January 23, 2018

Re: January 23, 2018

Re: January 23, 2018

Re: January 23, 2018

Re: January 23, 2018

Re: January 23, 2018

Re: January 23, 2018

Re: January 23, 2018

Re: January 23, 2018

Re: January 23, 2018

Re: January 23, 2018

Re: January 23, 2018