The New Sudoku Players' Forum

by **wapati** » Tue Oct 24, 2006 5:11 am

UR is a shortcut, still many, for we pattern watchers.

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

by **wapati** » Tue Oct 24, 2006 5:29 am

This one has lots. I would have waited, my file system has no pattern, it is now to post, or never. This is a good one.

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

by **Ocean** » Tue Oct 24, 2006 8:48 am

ravel wrote:Very interesting puzzle, Ocean. Maybe the hardest i have seen, which can be solved with basics + coloring, UR, swordfish and xy-wing. I only saw one redundant step (the last turbot fish), but (leaving out the tuples) the following remains:
UR4, 3 strong links, 2 SL (turbot fish or ER), swordfish, xy-wing

Thanks tarek, ravel, and wapati for comments and analysis of the "naked train" puzzle!

Carcul wrote:1. [r7c1]=6=[r7c6]-6-[r9c6]=6=[r6c1]-6-[r7c1], => r1c1<>6.

2. r6c2=9 or r7c6=9, and so r6c6<>9, solving the puzzle.

Thanks for the suggested chain for the "mixed colors" puzzle! It should be noted - at least for classification purposes - that the chain is not a simple nice loop, as the step : ...[r9c6]=6=[r6c1]... contains some hidden logic (elimination of 8 and 9 from r6c1 due to 'remote pairs', or 'xy-chain', or 'coloring', in the right direction, and a different argument ('naked pairs') in the left direction, is what I see - others might see something else).

by **Carcul** » Tue Oct 24, 2006 9:46 am

Wapati wrote:Seems to be a UR night! This one has two URs and a UR Loop and an x-wing and grouped x (skyscraper ER or Turbot, as you prefer!)

Code: Select all: *-----------------------------------------------------------* | 4 7 8 | 269 269 1 | 35 2369 2356 | | 5 6 2 | 79 8 3 | 19 4 17 | | 9 1 3 | 4 267 5 | 26 267 8 | |------------------+-------------------+--------------------| | 67 3 4 | 5 1267 267 | 126 8 9 | | 67 59 59 | 1267 3 8 | 246 1267 2467 | | 2 8 1 | 67 4 9 | 35 367 3567 | |------------------+-------------------+--------------------| | 8 459 59 | 1269 2569 246 | 7 12369 2346 | | 3 2 7 | 8 169 46 | 1469 5 146 | | 1 459 6 | 3 2579 247 | 8 29 24 | *-----------------------------------------------------------*

[r2c4]-9-[r2c7](-1-[r4c7])(-1-[r2c9]-7-[r56c9])=9=[r1c8]-9-[r9c8]-2-
-[r9c9]-4-[r4c7|r5c9]-6-[r6c9]-3,5-[r1c459]-9-[r2c4], => r2c4<>9 solving the puzzle.

Carcul

by **Carcul** » Tue Oct 24, 2006 3:46 pm

Wapati wrote:UR is a shortcut, still many, for we pattern watchers.

I don't see any shortcut with URs. Here's what I see:

Code: Select all: *-------------------------------------------------------------* | 17 9 137 | 4 156 1356 | 2 57 8 | | 5 68 4 | 2 7 18 | 9 3 16 | | 1278 678 12378 | 589 1589 1358 | 47 457 16 | |---------------------+--------------------+------------------| | 3 1 67 | 5679 569 567 | 8 2 4 | | 27 4 267 | 678 168 1678 | 5 9 3 | | 9 58 58 | 3 4 2 | 6 1 7 | |---------------------+--------------------+------------------| | 4 2 78 | 1 68 9 | 3 678 5 | | 178 3 1578 | 5678 2 5678 | 47 4678 9 | | 6 578 9 | 578 3 4 | 1 78 2 | *-------------------------------------------------------------*

[r7c3]=7=[r7c8]-7-[r1c8]=7=[r1c13]-7-[r23c2]-8-[r6c2]=8=[r6c3]-8-[r7c3], => r7c3<>8 solving the puzzle.

Carcul

by **ronk** » Tue Oct 24, 2006 4:33 pm

wapati, since most of the solutions being presented here use chains, I think you should remove the "NO CHAINS required" from the thread title ... like it was before.

by **ravel** » Tue Oct 24, 2006 6:31 pm

I dont see a contradiction. The chains normally lead to shorter solutions, but contrary to many other puzzles (possibly solvable with shorter chains) they are not needed.
btw for Ocean's naked train puzzle i could not find a solution with reasonable short chains, which lead to a shorter solution (less than 5 advanced steps), very unusual.

by **wapati** » Tue Oct 24, 2006 11:14 pm

This one has a lot of features. A swordfish early and then a finned sword where SE wants a forcing chain. ER/Turbots, xyz and xy as well.

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

by **wapati** » Wed Oct 25, 2006 3:32 am

This one varies a lot depending on the solver.
It is a busy one! (I didn't see swords or jellies tho.

)

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

by **Carcul** » Wed Oct 25, 2006 8:46 am

Ravel wrote:The chains normally lead to shorter solutions, but contrary to many other puzzles (possibly solvable with shorter chains) they are not needed.

So perhaps you will be kind enough to show me how you solve the following puzzle without chains:

Code: Select all: *-------------------------------------------------------------* | 17 9 137 | 4 156 1356 | 2 57 8 | | 5 68 4 | 2 7 18 | 9 3 16 | | 1278 678 12378 | 589 1589 1358 | 47 457 16 | |---------------------+--------------------+------------------| | 3 1 67 | 5679 569 567 | 8 2 4 | | 27 4 267 | 678 168 1678 | 5 9 3 | | 9 58 58 | 3 4 2 | 6 1 7 | |---------------------+--------------------+------------------| | 4 2 78 | 1 68 9 | 3 678 5 | | 178 3 1578 | 5678 2 5678 | 47 4678 9 | | 6 578 9 | 578 3 4 | 1 78 2 | *-------------------------------------------------------------*

Btw, I never said they were needed.

Carcul

by **Carcul** » Wed Oct 25, 2006 9:14 am

Wapati wrote:This one varies a lot depending on the solver.
It is a busy one! (I didn't see swords or jellies tho.

Code: Select all: *------------------------------------------------------------* | 12 2569 56789 | 1689 3 79 | 567 4 69 | | 67 469 6789 | 4689 467 5 | 3 2 1 | | 13 4569 35679 | 1469 2 479 | 567 59 8 | |---------------------+-------------------+------------------| | 23 26 36 | 459 457 479 | 1 8 49 | | 8 59 4 | 3 1 6 | 2 59 7 | | 57 1 579 | 49 8 2 | 45 6 3 | |---------------------+-------------------+------------------| | 456 7 56 | 2 9 1 | 8 3 46 | | 9 3 2 | 7 46 8 | 46 1 5 | | 46 8 1 | 456 456 3 | 9 7 2 | *------------------------------------------------------------*

[r1c6]-7-[r2c5|r34c6]-{ATILA(9): r3c268|r4c69|r5c8}-4,5-[r3c2]=4=
=[r2c2]-4-[r2c5]-6-[r2c1]-7-[r6c1]=7=[r6c3]=9=[r6c4]-9-[r2c4]=9=
=[r2c3]-9-[r3c23]-{TILA(9): r3c68|r4c69|r5c8}

and so r1c6<>7 solving the puzzle.

Carcul

by **ravel** » Wed Oct 25, 2006 9:37 am

Carcul wrote:So perhaps you will be kind enough to show me how you solve the following puzzle without chains:

Code: Select all: *-------------------------------------------------------------* | 17 9 137 | 4 156 1356 | 2 57 8 | | 5 68 4 | 2 7 18 | 9 3 16 | | 1278 678 12378 | 589 1589 1358 | 47 457 16 | |---------------------+--------------------+------------------| | 3 1 67 | 5679 569 567 | 8 2 4 | | 27 4 267 | 678 168 1678 | 5 9 3 | | 9 58 A58 | 3 4 2 | 6 1 7 | |---------------------+--------------------+------------------| | 4 2 AB78 | 1 68 9 | 3 678 5 | |B178 3 B1578 | 5678 2 5678 | 47 4678 9 | | 6 578 9 | 578 3 4 | 1 78 2 | *-------------------------------------------------------------*

Thanks for this grid, Carcul, it is the second time i see an ALS where the 2 sets have a common cell:
A={578}, B={1578}, x=5, z=7 => r9c2<>7
This solves the puzzle.
Of course we would have to discuss, if ALS is a non chaining technique, but this is not my thread.

I assume, there is a misconception, that you asked this question. Is this a puzzle from this thread?
Sorry, if i had expressed badly, what i mean. Wapati said, his puzzles can be solved without chains. This is nice to know for people, who dont like to use chains or who want to be sure, that it is not too hard for there skills. You and others showed, that with chains you can get shorter solutions and i like to see that (to see the non chain solution we can just look, how the solver programs do it).

by **wapati** » Wed Oct 25, 2006 10:08 am

Carcul wrote:
Ravel wrote:The chains normally lead to shorter solutions, but contrary to many other puzzles (possibly solvable with shorter chains) they are not needed.

So perhaps you will be kind enough to show me how you solve the following puzzle without chains:

Code: Select all
*-------------------------------------------------------------* | 17 9 137 | 4 156 1356 | 2 57 8 | | 5 68 4 | 2 7 18 | 9 3 16 | | 1278 678 12378 | 589 1589 1358 | 47 457 16 | |---------------------+--------------------+------------------| | 3 1 67 | 5679 569 567 | 8 2 4 | | 27 4 267 | 678 168 1678 | 5 9 3 | | 9 58 58 | 3 4 2 | 6 1 7 | |---------------------+--------------------+------------------| | 4 2 78 | 1 68 9 | 3 678 5 | | 178 3 1578 | 5678 2 5678 | 47 4678 9 | | 6 578 9 | 578 3 4 | 1 78 2 | *-------------------------------------------------------------*

Btw, I never said they were needed.

Carcul

If this was aimed at me, I do not post anything that I don't think I can solve. I can do a very few odd things that may be chains, none with confidennce. Colors, I have heard the term. If I posted it, I can show you what I thought works.

What is above does not seem familiar.

Just popping it into SodukoCue says 2 xys and 3 ERs. ERs can be Skyscrapers, Turbots or Kites. I can do those, they are patterns.

by **Carcul** » Wed Oct 25, 2006 10:50 am

Ravel wrote:it is the second time i see an ALS where the 2 sets have a common cell:
A={578}, B={1578}, x=5, z=7 => r9c2<>7
This solves the puzzle.

Thanks, very nice solution, although personaly it is easier to see the following ALSs:

A(5678)=r236c2, B(578)=r67c3, x=5, z=7, => r9c2<>7.

Ravel wrote:Is this a puzzle from this thread?

Yes, the one on the top of the current page.

Wapati wrote:Just popping it into SodukoCue says 2 xys and 3 ERs. ERs can be Skyscrapers, Turbots or Kites. I can do those, they are patterns.

Without wanting to start any controversial discussion, in my opinion XY- and XYZ-Wings, ERs, Turbots, Colors, are all chains. If one understands the principles of how to find nice loops, then there is no need to "memorize" all those names and methods, with the additional advantage of one being able to find other nice loops not "covered" by those techniques. Even Swordfish, a technique that perhaps I have only used one or two times in the sense of recognizing three rows or columns, can be expressed with nice loops. The same with ALSs. But, I understand that for many people is much more easier to look at those as standardized patterns.

Carcul

by **wapati** » Thu Oct 26, 2006 5:24 am

Carcul wrote:
Without wanting to start any controversial discussion, in my opinion XY- and XYZ-Wings, ERs, Turbots, Colors, are all chains.
Carcul

I don't do chains.

LOL, deep secret.

What methods cannot be expressed as chains ?

Thanks.

The New Sudoku Players' Forum

Fun puzzle. So many methods to solve. No CHAINS required.