The New Sudoku Players' Forum

by **Cenoman** » Sat Mar 27, 2021 8:50 pm

Weekly "extreme" puzzle (7.2), proposed by the site sudoku.org.uk

Code: Select all: +---+---+---+ |.5.|..7|.6.| |.3.|...|...| |6..|..5|3.4| +---+---+---+ |...|5..|4.2| |5..|...|..9| |9.4|.26|...| +---+---+---+ |3.2|1..|7.6| |...|...|.8.| |.7.|4..|.9.| +---+---+---+ .5...7.6..3.......6....53.4...5..4.25.......99.4.26...3.21..7.6.......8..7.4...9.

Edit 2: the true WE #757. Sorry

by **rjamil** » Sat Mar 27, 2021 9:57 pm

Work in progress (W-Ring move):

Code: Select all: ..3...1...4...15.....92..6......53...5.8.9.7...93......2..38.....46...2...6...4.. (Faulty one) +----------------------+----------+-----------------+ | 2679-8 679-8 3 | 5 68 4 | 1 89 2789 | | 269-8 4 (28) | 7 68 1 | 5 389 2389 | | 157(8) 17(8) 157(8) | 9 2 3 | 7(8) 6 4 | +----------------------+----------+-----------------+ | 14678 1678 178 | 2 17 5 | 3 1489 189 | | 3 5 1(2) | 8 4 9 | (2)6 7 16 | | 12478 178 9 | 3 17 6 | (28) 1458 158 | +----------------------+----------+-----------------+ | 1579 2 157 | 4 3 8 | 679 15 1567 | | 1589 1389 4 | 6 59 7 | 9-8 2 1358 | | 5789 3789 6 | 1 59 2 | 4 358 3578 | +----------------------+----------+-----------------+

Grouped W-Ring: 28 @ r2c3 r6c7 SL Row 5 between 2 @ r5c7 and 2 @ r5c3
SL Row 3 between 8 @ r3c123 and 8 @ r3c7 => -8 @ r1c12 r2c1 r8c7; stte

R. Jamil
----------
Cenomen Thanks for providing W-Ring example i/o True WE #757 (March 21-March 27) puzzle.
BTW, did you have a copy of Andrew Stuart's sudokuwiki.org WU#274, December 2 - December 8 puzzle?

by **Cenoman** » Sat Mar 27, 2021 11:08 pm

Hi rjamil,

The puzzle you have solved is one of the many mith's Pi-puzzles. You can find it in this thread (first puzzle)
I don't catch your question about Andrew's WU #274. The puzzle is available in your own link. What do you expect ?

by **rjamil** » Sat Mar 27, 2021 11:25 pm

Hi Cenoman,

Cenoman wrote:Hi rjamil,

The puzzle you have solved is one of the many mith's Pi-puzzles. You can find it in this thread (first puzzle)

Thanks for providing the original link of the first puzzle.

I don't catch your question about Andrew's WU #274. The puzzle is available in your own link. What do you expect ?

Actually, the link I provided contain weekly unsolvable from first, except WU #274 till site crashed.

R. Jamil

by **Leren** » Sun Mar 28, 2021 12:31 am

Code: Select all: *-------------------------------------------------* | 24 5 19 |a2-3Aa 34B 7 | 189 6 18 | | 24 3 179 | 68 68 1249Cf | 159 257 d157 | | 6 8 f179 | 29 19g 5 | 3 e27 4 | |-----------+--------------------+----------------| | 7 6 38 | 5 1389 139e | 4 13d 2 | | 5 2 38 | 378 13478 134D | 6 137 9 | | 9 1 4 |b37b 2 6 | 58 357c c578 | |-----------+--------------------+----------------| | 3 9 2 | 1 5 8 | 7 4 6 | | 1 4 56 | 23679 3679 239 | 25 8 35 | | 8 7 56 | 4 36 23 | 125 9 135 | *-------------------------------------------------* Kraken Row 3 Digit 1: 3 r1c4 - (3=7) r6c4 - r6c9 = r2c9 - r3c8 = 7 r3c3 - 1 r3c3 3 r1c4 - (3=4) r1c5 - r2c6 = 4 r5c6 - 1 r5c6; 3 r1c4 - r6c4 = r6c8 - (3=1) r4c8 - 1 r4c6 *= r2c6 - 1 r3c5; => - 3 r1c4; stte

Leren

by **jco** » Sun Mar 28, 2021 2:24 am

I found a solution in two steps.
After basics

Code: Select all: .-------------------------------------------------. | 24 5 19 |a23 34 7 | 189 6 18 | | 24 3 179 | 68 68 1249 | 159 c257 157 | | 6 8 179 |a9-2 19 5 | 3 d27 4 | |------------+--------------------+---------------| | 7 6 38 | 5 1389 139 | 4 13 2 | | 5 2 38 | 378 13478 134 | 6 137 9 | | 9 1 4 |b37 2 6 | 58 c357 578 | |------------+--------------------+---------------| | 3 9 2 | 1 5 8 | 7 4 6 | | 1 4 56 | 23679 3679 239 | 25 8 35 | | 8 7 56 | 4 36 23 | 125 9 135 | '-------------------------------------------------'

1. (9=23)r13c4-(3)r6c4=(3-52)r26c8=(2)r3c8 => -2 r3c4 (+4 placements)

Code: Select all: .-------------------------------------------------. | 24 5 19 | e23 34 7 | 189 6 18 | | 24 3 19 | 68 68 a4-2 | 159 57 157 | | 6 8 7 | 9 1 5 | 3 2 4 | |-----------+--------------------+----------------| | 7 6 38 | 5 389 139 | 4 13 2 | | 5 2 38 | 378 3478 b134 | 6 b137 9 | | 9 1 4 | d37 2 6 | 58 c357 c578 | |-----------+--------------------+----------------| | 3 9 2 | 1 5 8 | 7 4 6 | | 1 4 56 | 2367 3679 239 | 25 8 35 | | 8 7 56 | 4 36 23 | 125 9 135 | '-------------------------------------------------'

2. (4)r2c6=(4-17)r5c68=(7)r6c89-(7=32)r16c4 => -2 r2c6; ste

Edit: improved writing of chains.

Website · by **denis_berthier** » Sun Mar 28, 2021 4:05 am

.
Resolution state after Singles and whips[1]:

Code: Select all: 24 5 19 2389 13489 7 189 6 18 24 3 179 2689 14689 1249 1589 257 1578 6 8 179 29 19 5 3 27 4 7 6 38 5 1389 139 4 13 2 5 2 38 378 13478 134 6 137 9 9 1 4 37 2 6 58 357 578 3 9 2 1 5 8 7 4 6 1 4 56 23679 3679 239 25 8 35 8 7 56 4 36 23 125 9 135

1) A simple solution can be obtained with reversible chains no longer than 4:

Code: Select all: naked-triplets-in-a-row: r1{c3 c7 c9}{n1 n9 n8} ==> r1c5 ≠ 9, r1c5 ≠ 8, r1c5 ≠ 1, r1c4 ≠ 9, r1c4 ≠ 8 whip[1]: r1n8{c9 .} ==> r2c7 ≠ 8, r2c9 ≠ 8 hidden-pairs-in-a-row: r2{n6 n8}{c4 c5} ==> r2c5 ≠ 9, r2c5 ≠ 4, r2c5 ≠ 1, r2c4 ≠ 9, r2c4 ≠ 2 biv-chain[3]: r6c4{n7 n3} - b2n3{r1c4 r1c5} - c5n4{r1 r5} ==> r5c5 ≠ 7 hidden-single-in-a-column ==> r8c5 = 7 z-chain[3]: r5c3{n3 n8} - r5c4{n8 n7} - r6c4{n7 .} ==> r5c5 ≠ 3 z-chain[3]: r5c3{n3 n8} - r5c4{n8 n7} - r6c4{n7 .} ==> r5c6 ≠ 3 biv-chain[4]: r3c8{n2 n7} - c9n7{r2 r6} - r6c4{n7 n3} - r1c4{n3 n2} ==> r3c4 ≠ 2 singles ==> r3c4 = 9, r3c5 = 1, r3c3 = 7, r3c8 = 2, r4c5 = 9, r4c3 = 8, r5c3 = 3, r8c6 = 9 biv-chain[3]: r1c4{n3 n2} - c6n2{r2 r9} - c6n3{r9 r4} ==> r6c4 ≠ 3 stte

There are 8 W1-anti-backdoors:

Code: Select all: n8r6c7 n3r6c4 n4r5c6 n4r2c1 n8r1c9 n4r1c5 n3r1c4 n2r1c1

Five of them lead to a single step solution.

2) The simplest single-step solution by whips can be obtained using a whip[7]:

Code: Select all: whip[7]: r1n3{c5 c4} - r6c4{n3 n7} - r5n7{c5 c8} - r3n7{c8 c3} - r3n1{c3 c5} - r5n1{c5 c6} - r5n4{c6 .} ==> r1c5 ≠ 4 stte

4 other single-step solutions can be obtained with longer whips:

Code: Select all: whip[8]: r1n4{c1 c5} - r1n3{c5 c4} - r6c4{n3 n7} - r5n7{c5 c8} - r3n7{c8 c3} - r3n1{c3 c5} - r5n1{c5 c6} - r5n4{c6 .} ==> r2c1 ≠ 4 stte OR whip[8]: r6c4{n3 n7} - r5n7{c5 c8} - r3n7{c8 c3} - r3n1{c3 c5} - r5n1{c5 c6} - r5n4{c6 c5} - r1n4{c5 c1} - r1n2{c1 .} ==> r1c4 ≠ 3 stte OR whip[8]: r1n4{c1 c5} - r1n3{c5 c4} - r6c4{n3 n7} - r5n7{c5 c8} - r3n7{c8 c3} - r3n1{c3 c5} - r5n1{c5 c6} - r5n4{c6 .} ==> r1c1 ≠ 2 stte OR whip[10]: r1n3{c4 c5} - r1n4{c5 c1} - r1n2{c1 c4} - r3c4{n2 n9} - r3c5{n9 n1} - r2c6{n1 n4} - c5n4{r2 r5} - c5n7{r5 r8} - r8c4{n7 n6} - r9c5{n6 .} ==> r6c4 ≠ 3

stte

by **RSW** » Sun Mar 28, 2021 8:44 am

Code: Select all: +-----------+--------------------+-------------+ |a24 5 19 | b23 c34 7 | 189 6 18 | | 24 3 179 | 68 68 1249 | 159 257 157 | | 6 8 g179 | 29 g19 5 | 3 f27 4 | +-----------+--------------------+-------------+ | 7 6 38 | 5 1389 139 | 4 13 2 | | 5 2 e38 |cd378 def13478 134 | 6 e137 9 | | 9 1 4 | c37 2 6 | 58 357 578 | +-----------+--------------------+-------------+ | 3 9 2 | 1 5 8 | 7 4 6 | | 1 4 56 | 23679 3679 239 | 25 8 35 | | 8 7 56 | 4 36 23 | 125 9 135 | +-----------+--------------------+-------------+

Nishio net
2r1c1? > 3r1c4 > (7r6c4, 4r1c5, -3r5c4 ) > (-47r5c5, 8r5c4) > (-8r5c5, 3r5c3, 7r5c8) > (1r5c5, 2r3c8) > (9r3c5, 1r3c3) > -7r3! => 4r1c1; stte

by **pjb** » Sun Mar 28, 2021 12:05 pm

Code: Select all: 24 5 19 | 2-3 j34 7 | 189 6 18 24 3 179 | 68 68 i1249 | 159 257 157 6 8 e179 | 29 f19 5 | 3 d27 4 ------------------------+-----------------------+--------------------- 7 6 38 | 5 189-3 139 | 4 13 2 5 2 38 |b378 gb1478-3 h134 | 6 c137 9 9 1 4 |a37 2 6 | 58 357 578 ------------------------+-----------------------+--------------------- 3 9 2 | 1 5 8 | 7 4 6 1 4 56 | 23679 3679 239 | 25 8 35 8 7 56 | 4 36 23 | 125 9 135

(3=7)r6c4 - (7)r5c45 = (7)r5c8 - (7)r3c8 = (7-1)r3c3 = (1)r3c5 - (1)r5c5*8 = (1-4)r5c6 = (4)r2c6 - (4=3)r1c5 => -3 r1c4, r45c5; stte

Phil

by **SteveG48** » Sun Mar 28, 2021 4:56 pm

Code: Select all: *---------------------------------------------------------------------* | 24 5 19 | 2-3 h34 7 | 189 6 18 | | 24 3 179 | 68 68 1249 | 159 257 157 | | 6 8 179 |e29 e19 5 | 3 de27 4 | *----------------------+-----------------------+----------------------| | 7 6 38 | 5 f189-3 f139 | 4 de13 2 | | 5 2 38 | 378 fh1478-3 g134 | 6 c137 9 | | 9 1 4 |a37 2 6 |c58 bc357 bc578 | *----------------------+-----------------------+----------------------| | 3 9 2 | 1 5 8 | 7 4 6 | | 1 4 56 | 23679 3679 239 | 25 8 35 | | 8 7 56 | 4 36 23 | 125 9 135 | *---------------------------------------------------------------------*

(3=7)r6c4 - 7r6c89 = ((583)r6c789)&(7r5c8) - (3|7)r34c8 = ((291)r3c458)&(1r4c8) - 1b5p235 = (1-4)r5c6 = (43)r1c5 => -3 r1c4,r45c5 ; stte

by **SteveG48** » Sun Mar 28, 2021 5:03 pm

Looks like mine and Phil's are almost the same. Who woulda thunk it?

by **Cenoman** » Mon Mar 29, 2021 4:20 pm

SteveG48 wrote:Looks like mine and Phil's are almost the same. Who woulda thunk it?

Hi Steve,
You use quite the same cells, with slight differences:
-Phil's is a memory chain [weak link (7-1)r5c8] while your AIC uses the AALS r34c8, and eventually, Phil uses the strong link (1)r5c58=r5c6 while you use (1)b5p235=b5p6.

In the same vein, I had the following:

Code: Select all: +------------------+-------------------------+--------------------+ | 24 5 19 | b23 dc34 7 | 189 6 18 | | 24 3 179 | 6-8 e68 1249 | 159 257 157 | | 6 8 179 | 29 19 5 | 3 27 4 | +------------------+-------------------------+--------------------+ | 7 6 38 | 5 1389 139 | 4 13 2 | | 5 2 38 | a378 e13478 134 | 6 137 9 | | 9 1 4 | a37 2 6 | 58 357 578 | +------------------+-------------------------+--------------------+ | 3 9 2 | 1 5 8 | 7 4 6 | | 1 4 56 | 2369-7 e3679 239 | 25 8 35 | | 8 7 56 | 4 ed36 23 | 125 9 135 | +------------------+-------------------------+--------------------+

(78=3)r56c4 - r1c4 = r1c5 - (3r9c5 | 4r1c5) = (68r29c5 & 47r58c5) => -8 r2c4, -7r8c4; ste

by **SteveG48** » Mon Mar 29, 2021 8:26 pm

Cenoman wrote:(78=3)r56c4 - r1c4 = r1c5 - (3r9c5 | 4r1c5) = (68r29c5 & 47r58c5) => -8 r2c4, -7r8c4; ste

Oooh, that's nice!

The New Sudoku Players' Forum

WE #757 (March 21-March 27)

WE #757 (March 21-March 27)

Re: WE #757 (March 21-March 27)

Re: WE #757 (March 21-March 27)

Re: WE #757 (March 21-March 27)

Re: WE #757 (March 21-March 27)

Re: WE #757 (March 21-March 27)

Re: WE #757 (March 21-March 27)

Re: WE #757 (March 21-March 27)

Re: WE #757 (March 21-March 27)

Re: WE #757 (March 21-March 27)

Re: WE #757 (March 21-March 27)

Re: WE #757 (March 21-March 27)

Re: WE #757 (March 21-March 27)