The New Sudoku Players' Forum

by **re'born** » Sun Feb 18, 2007 3:49 pm

Carcul wrote:
ArkieTech wrote:Here is a puzzle I found in a book. It was marked easy. I found it anything but. Can anyone find an easy solution for it?

The type-1 UR in cells r68c78 sets r8c7=7 solving the puzzle.

Carcul

To be fair, I think you'll find your solution to be identical to the one I gave above.

by **udosuk** » Sun Feb 18, 2007 4:47 pm

Rest assured rep'nA... Although ArkieTech didn't notice and thank the correct original helper, the rest of the followers of this thread (like me) surely recognise your ingenuity and helpfulness in demonstrating your great moves...

rep'nA wrote:How about this? There is a skyscraper on <1>. Then you can color the 4's to get an exclusion which reveals a finned x-wing. Finally an XYZ-wing (revealed by the first skyscraper and locked candidates) will solve the puzzle. Hopefully this doesn't give too much away, but gives a road map.

From your "road map", I did deduce a solution without using the Uniqueness Loop/BUG-lite, but the order was slightly different, as below:

Code: Select all: *-----------------------------------------------------------* | 147 6 5 | 148 9 2 | 3 47 48 | | 8 79 *14 |#134 6 *34 | 2 79 5 | | 3 29 24 | 7 5 -48 | 6 1 489 | |-------------------+-------------------+-------------------| | 17 137 6 | 48 134 4789 | 5 49 2 | | 5 4 8 | 29 12 6 | 19 3 7 | | 9 237 123 | 45 134 57 | 8 6 14 | |-------------------+-------------------+-------------------| | 6 5 7 | 29 24 1 | 49 8 3 | | 14 8 9 | 35 7 35 | 14 2 6 | | 2 13 *134 | 6 8 *49 | 7 5 19 | *-----------------------------------------------------------* finned x-wing on 4s r29c36 with fin r2c4 -> r3c6<>4 r3c6=8 -> r1c9=8, r4c4=8 simple colours on 1s -> r6c3<>1 locked candidates on 1s -> r4c5<>1 xyz-wing on 1,3,4 -> r6c4<>4 simple colours on 4s will solve the puzzle now

However, I'm still puzzled about how keith resolved this position

:

Code: Select all: *-----------------------------------------------------------* | 147 6 5 | 148 9 2 | 3 47 48 | | 8 179 14 | 1345 6 345 | 2 479 459 | | 3 29 24 | 7 45 458 | 6 1 4589 | |-------------------+-------------------+-------------------| | 17 137 6 | 48 134 4789 | 5 49 2 | | 5 4 8 | 29 12 6 | 19 3 7 | | 9 237 123 | 45 1345 57 | 8 6 14 | |-------------------+-------------------+-------------------| | 6 5 7 | 29 24 1 | 49 8 3 | | 14 8 9 | 35 7 35 | 14 2 6 | | 2 13 134 | 6 8 49 | 7 5 19 | *-----------------------------------------------------------*

In particular, how can we conclude r3c5=5 and not 4? :?:

by **keith** » Sun Feb 18, 2007 7:59 pm

There is a Type 3 UR on <35> in R28C46. It takes out <1> in R2C2 and <4> in R2C89. That reveals a pair <79> and solves R2C9 as 5.

So, you have this:

Code: Select all: +----------------+----------------+----------------+ | 147 6 5 | 148 9 2 | 3 47 48 | | 8 79 14 | 134 6 34@ | 2 79 5 | | 3 29 24 | 7 45@ 458# | 6 1 489 | +----------------+----------------+----------------+ | 17 137 6 | 48 134 4789 | 5 49 2 | | 5 4 8 | 29 12 6 | 19 3 7 | | 9 237 123 | 45 1345 57 | 8 6 14 | +----------------+----------------+----------------+ | 6 5 7 | 29 24 1 | 49 8 3 | | 14 8 9 | 35 7 35@ | 14 2 6 | | 2 13 134 | 6 8 49 | 7 5 19 | +----------------+----------------+----------------+

The XY-wing labelled @ takes out <5> from #, leaving R3C5 as the only place for <5> in R3.

Keith

PS: Let me explain the UR better. In this row

Code: Select all: | 8 179 14$ | 1345% 6 345% | 2 479 459& |

at least one of the cells marked % must be <1> or <4>, as must the cell marked $. There are no other places in the row for <14> to go.

There is also a Type 4 reduction: In the row, one of the cells marked % cannot be <3> or <5>. The only possibility is that & is <5>. Then, there is a triple <134> that clears the <1> and <4> as before.

by **udosuk** » Sun Feb 18, 2007 8:13 pm

Thanks Keith for explaining...

So, after all, is there any possible way of solving this one without any uniqueness assumption as well as forcing chains? :?:

by **ArkieTech** » Sun Feb 18, 2007 9:17 pm

Rest assured rep'nA... Although ArkieTech didn't notice and thank the correct original helper, the rest of the followers of this thread (like me) surely recognise your ingenuity and helpfulness in demonstrating your great moves...

My appolgies to anyone missed for showing me what I missed from the start, the unique rectangle. Thanks to all. I hope to learn to be more observant.

by **re'born** » Sun Feb 18, 2007 9:49 pm

ArkieTech wrote:
udosuk wrote:Rest assured rep'nA... Although ArkieTech didn't notice and thank the correct original helper, the rest of the followers of this thread (like me) surely recognise your ingenuity and helpfulness in demonstrating your great moves...

My appolgies to anyone missed for showing me what I missed from the start, the unique rectangle. Thanks to all. I hope to learn to be more observant.

Thank you udosuk for the kind words. ArkieTech, no apology necessary. I woke up on the wrong side of the bed this morning. I'm sorry for the rather bush league petty post.

by **keith** » Sun Feb 18, 2007 9:54 pm

rep'nA wrote:If you want a fun solution, try some Medusa coloring starting at say r1c8. You pretty much destroy the puzzle ...

Can you point me to an explanation of what "Medusa Coloring" is?

By the way, that unique swordfish is the analog of a Type 6 Unique Rectangle (which is a unique X-wing). Quite a rare creature, I imagine!

I eventually solved the puzzle by coloring on <4> to make two exclusions in Box 1, which solves R2C3 as <4>, and you are done.

Keith

by **re'born** » Sun Feb 18, 2007 10:09 pm

keith wrote:
rep'nA wrote:If you want a fun solution, try some Medusa coloring starting at say r1c8. You pretty much destroy the puzzle ...

Can you point me to an explanation of what "Medusa Coloring" is?

The place I saw it was Ruud's Sudoku Solving Guide, but I think it goes under the name advanced coloring or ultra coloring in other places. Check Mike Barker's list for some links.

keith wrote:By the way, that unique swordfish is the analog of a Type 6 Unique Rectangle (which is a unique X-wing). Quite a rare creature, I imagine!

I don't recall seeing one before, but then again, I've never looked for it before. In any case, it is a really cool find.

by **wapati** » Sun Feb 18, 2007 10:53 pm

This one I don't think I'd solve on paper because I'd give up. <sigh>

Early finned JellyFish involves a lot of candidates!

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

by **wapati** » Mon Feb 19, 2007 4:06 am

This one has an early Finned Jelly also!

Code: Select all: . 9 . | . 3 4 | . . 5 8 . . | . . . | 4 . . . . . | . . 5 | 1 6 . --------------------- . . . | . 8 . | 5 . 3 3 . . | 5 . 9 | . . 1 5 . 4 | . 6 . | . . . --------------------- . 8 5 | 9 . . | . . . . . 6 | . . . | . . 8 1 . . | 4 2 . | . 5 .

by **Carcul** » Mon Feb 19, 2007 11:28 am

Wapati wrote:This is "thorny".

Code: Select all: *-------------------------------------------------------* | 147 6 5 | 148 9 2 | 3 47 48 | | 8 179 14 | 1345 6 345 | 2 479 459 | | 3 29 24 | 7 45 458 | 6 1 4589 | |-----------------+------------------+------------------| | 17 137 6 | 48 134 4789 | 5 49 2 | | 5 4 8 | 29 12 6 | 19 3 7 | | 9 1237 123 | 45 1345 457 | 8 6 14 | |-----------------+------------------+------------------| | 6 5 7 | 29 24 1 | 49 8 3 | | 14 8 9 | 35 7 35 | 14 2 6 | | 2 13 134 | 6 8 49 | 7 5 19 | *-------------------------------------------------------*

[r1c1]=7=[r1c8]-7-[r2c8]-{Nice Loop: [r9c3]-4-[r2c3]-1-[r2c46]-4-[r2c8]
=4=[r4c8]=9=[r5c7]=1=[r8c7]=4=[r8c1]-4-[r9c3]}-4-[r9c3]=4=[r8c1]-4-
-[r1c1], => r1c1<>4 and the puzzle is solved.

Carcul

by **ravel** » Mon Feb 19, 2007 2:07 pm

wapati wrote:This one I don't think I'd solve on paper because I'd give up. <sigh>

Early finned JellyFish involves a lot of candidates!

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

With locked candidates you come here:

Code: Select all: *----------------------------------------------------------* | 58 4 178 |#357 6 2 |#13578 9 578 | | 9 157 3 | 4 18 158 | 15678 1568 2 | | 258 6 1278 | 357 1389 13589 | 4 #1358 578 | |------------------+-------------------+-------------------| | 458 2 48 | 9 7 6 | 158 158 3 | | 7 35 68 | 1 38 4 | 2 568 9 | | 1 39 689 | 2 5 38 | 68 7 4 | |------------------+-------------------+-------------------| | 346 179 5 |#36 1349 139 | 378 2 678 | | 2346 8 24 |#356 -34 7 | 9 #35 1 | | 36 179 179 | 8 2 1359 | 357 4 567 | *----------------------------------------------------------*

Here the "triple around the corner" 356 both allows an xyz-wing elimination (r8c5<>3) and is part of an
easy-to-spot chain with the 2 strong links for 3 (wasn't it called turbot chain ?)
r1c7<>3 => r3c8=3 => r8c8=5 => r78c4=36 => r1c4<>3 => r1c7=3
So r1c7=3 and the puzzle can be solved with another xyz- and 2 xy-wings.

Note that also the second xyz-wing is part of a short chain (the 5's are strongly linked here):

Code: Select all: *-------------------------------------------------------* |#58 4 78 | 7 6 2 | 3 9 #58 | | 9 57 3 | 4 18 158 | 1678 168 2 | | 2 6 #78 | 3 189 1589 | 4 1-8 #578 | |---------------+-------------------+-------------------|

r3c3=8 => r3c9=7 => r1c9=5 => r1c1=8, so r3c3=7.
With r3c8<>8 from the xyz-wing the puzzle is solved then without the xy-wings.

by **wapati** » Tue Feb 20, 2007 9:13 pm

This is (I think) the toughest pattern puzzle I have generated.

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

by **ravel** » Wed Feb 21, 2007 10:50 am

wapati wrote:This is (I think) the toughest pattern puzzle I have generated.

A lot of fish in there, i think i had 5 turbot fish, a finned x-wing, three times 3 strong links and this creature, i cannot identify:

Code: Select all: ----------------------- 4 . . | 4 4 . | . 4 4 . . . | 4 . . | . . 4 . . 4 | .-4 . | . 4 4 ----------------------- 4 4 . | 4 . . | . . 4 4 . . | . 4 . | . .-4 4 . . |-4 . . | . 4 4 ----------------------- . . . | . . 4 | . . . . . . | . . . | 4 . . . 4 4 | . . . | . . . -----------------------

Added: 2 are from empty rectangles, but r3c5?

by **daj95376** » Wed Feb 21, 2007 1:10 pm

Code: Select all: # Empty Rectangle [r2b6] *--------------------------------* | 4 . . | 4 4 . | . 4 4 | | . . . | 4 . . | . . 4 | | . . 4 | . 4 . | . 4 4 | |----------+----------+----------| | 4 4 . | 4 . . | / / 4 | | 4 . . | . 4 . | / / 4 | | 4 . . |-4 . . | . 4 4 | |----------+----------+----------| | . . . | . 4 . | . . . | | . . . | . . . | 4 . . | | . 4 4 | . . . | . . . | *--------------------------------*

Code: Select all: # ??? Jellyfish r1256/c1589 *--------------------------------* |*4 . . |#4 *4 . | . *4 *4 | | . . . |#4 . . | . . *4 | | . . 4 | . -4 . | . 4 4 | |----------+----------+----------| | 4 4 . | 4 . . | . . 4 | |*4 . . | . *4 . | . . *4 | |*4 . . | . . . | . *4 *4 | |----------+----------+----------| | . . . | . 4 . | . . . | | . . . | . . . | 4 . . | | . 4 4 | . . . | . . . | *--------------------------------*

Kraken Jellyfish w/remote cell if you don't perform ER first.

The New Sudoku Players' Forum

CHAINS, not required. Good puzzles.

Medusa Coloring?

Re: Medusa Coloring?

Another Solution for the "Thorny" Puzzle