The New Sudoku Players' Forum

by **wapati** » Sat May 22, 2010 3:10 pm

Wapati here,

I posted puzzles needing no chains for a spell.

I have better understanding now and admit that chains are hard to avoid.

I now prefer short chains, I guess I always did. I still really like swordfish and jellyfish.

I have resumed posting puzzles that I think are fun. Big fish, maybe short chains, will be involved.

Great to be back in the hands of people who care about Sudoku, huge thanks to Jason and GSF.

I use HoDoKu, JSudoku and SudoCue every day. There are other fine solvers that I use less often.
I admire and enjoy the work all people who create fine apps and I thank them.

I do most solving with pencil and paper but my selection of which puzzles is determined using software.
It is great that I have options when/if I get a brain clamp!

by **wapati** » Sat May 22, 2010 3:13 pm

by **wapati** » Sat May 22, 2010 3:23 pm

#1

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

by **wapati** » Sat May 22, 2010 3:30 pm

It would be good to know about hidden URs, else, perhaps you like long xy-chains? :lol:

#2

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

by **wapati** » Sun May 23, 2010 4:46 am

There is stuff here. Sashimi sword is why I like this one.
Towards finished? There is an almost W-wing where you need to see that a pair ( 56 46 ) can be used as a ( 45 ).
Seems easy to me. 8-)

#3

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

by **wapati** » Mon May 24, 2010 12:30 am

Hidden UR, swordfish.

#4

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

by **eleven** » Tue May 25, 2010 10:52 am

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

Hi wapati,
it seems that there are not much players around here

As a start to your first one (please give them numbers for references), its very easy and does not need any fish.
After singles:

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

The marked cells can only be 16, so there is a remote pair r7c2-r3c8 and also r7c2-r8c9 (via r23c9). Thus r8c3 cannot be 16, and the 1 in r7c2 solves it with singles again.

[Added:]
Last puzzle (#4):
After a few singles:

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

The #-cells form a possibly deadly pattern (UR) for 6 and 8. Since 6 cannot be elsewhere in the 2 rows, either 8 must be in r1c789 or in r6c7.
In both cases it cannot be in r3c7. Since there is a hidden pair 25 in r23c8, r3c5 must be 8 - only singles left.

by **wapati** » Wed May 26, 2010 4:22 am

Interesting solving methods, eleven. Thanks for showing them!

Finned Swordfish. #5

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

by **eleven** » Wed May 26, 2010 7:55 am

This time a dirty chain :geek:

After singles:

Code: Select all: . 9 3 | 1 . . | 8 . 2 . . . | . . 8 | . . 9 . @48 . | 9 . 6 | 7 3 1 ------------+---------+-------- #279 5 #27 | 6 .*24 | 1 8 . 1 *68 28 | 7 29 3 | . . 5 *69 3 4 | 5 8 1 |69 2 7 ------------+---------+-------- @4+ 2 9 | 8 1 *4+|35 57 6 8 17 . |23 6 . | . . 4 . -47 6 |34 . 9 | 2 1 8

Arans "hidden pair":
Either there is a pair 27 in r4c13, implying 4 in r4c6
Or there is a 9 in r4c1, leading to a 4 in r3c2 via r6c1=6,r5c2=8
So we have r3c2=4 or r4c6=4, which also implies r7c1=4 (via r7c6<>4)
And we can eliminate 4 in r9c2 (and r123c1).

by **wapati** » Thu May 27, 2010 2:23 pm

Finned Jelly.

#6

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

by **wapati** » Sat May 29, 2010 2:14 am

Finned sword

#7

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

by **eleven** » Sat May 29, 2010 11:01 pm

Puzzle 6:

With singles and box-line for 6 in c4 you get here:

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

The 4 # marked cells only can be 24, thus there is a remote pair in r4c4 and r1c9, eliminating 24 in r1c4 (leaving 16).
But there is more: 2/4 in r1c9 also implies 2/4 in r3c123. So you can eliminate 24 also in r3c4, leaving 6 alone, because the 8 also is locked in r3c123.
Singles after that move.

Puzzle 7 was a long one for me.

After singles:

Code: Select all: 9 6 2|8 5 3|1 7 4 5 8 .|. . 4|3 2 6 # 3 4|6 2 @|p p 8 -----+-----+----- . . .|7 8 5|6 . . . . .|. 6 .|. . . . . 6|3 4 2|Â° p . -----+-----+----- 4 . .|5 1 6|. 8 . - 1 5|2 @ 8|4 6 . 6 2 8|4 3 #|. 1 5

In row 3 17 is left in the marked cells. With the strong link for 7 in box 8 we have a kite eliminating 7 in r8c1, leaving 3.
Also note the UR 59 (p) in r36c78 leaving 78 in r6c7.

Code: Select all: 9 6 2|8 5 3|1 7 4 5 8 @|. # 4|3 2 6 # 3 4|6 2 @|. . 8 -----+-----+----- 12 . .|7 8 5|6 . . 78 . .|. 6 .|. . 27 . . 6|3 4 2|78. . -----+-----+----- 4 . .|5 1 6|2 8 3 3 1 5|2 @ 8|4 6 # 6 2 8|4 3 #|@ 1 5

Now we can find more with those 7's. With the strong links either all # cells must be 7 or all @ cells.
So one of r1c3 and r9c7 must be 7, implying r5c1=8 and r6c7=8 resp. Since one leads to the other, both must be true.
Since r3c1=17, either r3c1=1 implying r4c1=2 or (r3c1 and) r8c9=7 implying r5c9=2. Again one 2 leads to the other.

This gives

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

and new strong links for 7 in columns 1, 7 and 9. Now the @-marked cells cannot be 7, because there are two in row 6.

by **aran** » Tue Jun 01, 2010 11:49 am

Eleven in #7 from the position just after the UR move <59>, one could use this :
9r2c5+7r8c9 impossible (=>r8c5 empty)
=>7r2c3+9r4c9 impossible (=>previous)
=>1r2c3 or pair12r4c19 must be true
so r4c3 <1> therefore r3c1=7.
Even though this is really hidden pair logic, this expression of it might be more in your line of thought.

by **eleven** » Tue Jun 01, 2010 1:18 pm

Nice, i had missed the implication r4c19=12 -> r2c3=1
Both r4c9=9 and r2c3=1 imply 7 in a #-cell.

by **wapati** » Wed Jun 02, 2010 12:36 am

Interesting finned jelly, it can be seen differently at right angles.
(You often see a swordfish instead. )
Use it, it is a shortcut. Added to a remote pair you can solve this.

There are lots of herring. :-)

#8

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

The New Sudoku Players' Forum

Big fish

Big fish

Short form of these puzzles.

#1

#2

#3

#4

Re: Big Fishies

#5

Re: Big fish

Finned Jelly.

Finned Swordfish

Re: Big fish

Re: Big fish

Re: Big fish

Finned Jelly. #8