## Discussion...

Post an idea here...

## ... by: Frans Goosens

With trial and error

I have decided to calculate cell A3 and cell G9 all combinations

A3=123 G9=139

A3=1 G9=1 Wrong. Undo calculation

A3=1 G9=3 Wrong, Undo calculation

A3=1 G9=9 Wrong, Undo calculation

A3=2 G9=1 Solved,

#299

982 764 513

731 852 496

645 139 728

593 476 182

824 591 367

176 283 945

469 327 851

257 918 634

318 645 279

## ... by: SteveJ

Requires two guesses. No single guess is sufficient, or a single level of recursion would have solved it.

stevej@bsd84:~/sudoku % ./sudoku -f ./puzzles/un-1.txt -s 2 -r -D 1

*** ./puzzles/un-1.txt not solved, sane! Solution failed!

Iterations: 2. Changes: Rows 136, cols 99, squares 32, tot 267

dfs: cells 59 vals 264 rec 264 bt 264 ns 0 mrl 1

stevej@bsd84:~/sudoku %

stevej@bsd84:~/sudoku % ./sudoku -f ./puzzles/un-1.txt -s 2 -r -D 2

>>>>>> ./puzzles/un-1.txt solved, sane!

Iterations: 13. Changes: Rows 205, cols 180, squares 83, tot 468

dfs: cells 3417 vals 14418 rec 13819 bt 13818 ns 598 mrl 2

stevej@bsd84:~/sudoku %

## ... by: Frans Goosens

U.C means Undo calculation.

I have decided to calculate the cells C2 and G8

C2=4 G8=1 Wrong. U.C

C2=4 G8=2 Wrong, U.C

C2=4 G8=8 Wrong, U.C

C2=5 G8=1 Wrong, U.C

C2=5 G8=2 Solved,

#294

623 471 859

478 659 231

159 283 647

245 916 378

731 528 964

896 347 512

384 195 726

517 862 493

962 734 185
## ... by: Don

Simplest Unsolvable Sudoku

1 0 0 0 0 0 0 0 0

0 0 0 1 0 0 0 0 0

0 0 0 0 0 0 1 0 0

0 1 0 0 0 0 0 0 0

0 0 0 0 1 0 0 0 0

0 0 0 0 0 0 0 1 0

0 0 1 0 0 0 0 0 0

0 0 0 0 0 1 0 0 0

0 0 0 0 0 0 0 0 2

Many variations possible.

Don
## ... by: RICHARD ALLAN

Even using logic,I had to make about ten 1/2 guesses and the puzzle still took me about 3 hours to solve,what a stinker.The 6x6 puzzle yesterday was easy compared to this one.Once you found all the 5s,the problem was solved.
## ... by: Duder Sud

Use 7 in A6 then use solver
## ... by: Sarah

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Sarah
## ... by: jjflip

dude, your slover blows! its WAYYYYY to complicted. i tried another solver and it worked pretty quick
## ... by: Solved? Or Not..

Is this right?

[6, 2, 5, 1, 7, 8, 9, 4, 3]

[9, 4, 8, 3, 2, 6, 1, 5, 7]

[3, 7, 1, 9, 4, 5, 8, 6, 2]

[2, 5, 7, 6, 1, 9, 3, 8, 4]

[4, 6, 3, 5, 8, 7, 2, 9, 1]

[1, 8, 9, 4, 3, 2, 5, 7, 6]

[7, 9, 2, 8, 6, 3, 4, 1, 5]

[5, 1, 6, 2, 9, 4, 7, 3, 8]

[8, 3, 4, 7, 5, 1, 6, 2, 9]

Thanks!
## ... by: JULIEN

ok I did this Sudoku but there is a mistake and it is why it is impossible, the 9 in b1 should be at c2 therefore 7 c2 should be at b1. here the solution without the misplacement of this 2 number:

652-138-947

734-296-158

198-745-326

247-619-583

561-483-279

389-572-461

923-864-715

416-957-832

875-321-694

this is the one and only solution, the person who did invent this Sudoku put an error to be impossible...

but now with this 2 number put back at their right place now it is possible ( see result above).

it took me 4 hours but I find it.

roncq@hotmail.co.uk

## ... by: saskjals

dadadssada
## ... by: newby

first finding all the 3 number sets, (3,5,8)C7 was most interesting as it offered the most paired sets using 8C7.

The using pairs (2,9)J8,J9; (1,8)H9,G8; (4,7)G7, H7

9J9, 8H9, 7H7 solves!!
## ... by: Enes

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## ... by: marcel hendrix

This one takes 0.061 ms to solve. That is not much, compared to 2.5 ms for Arto Inkala's idea, or some samples from sudoku17.txt (326 ms for line 527, 989 ms for line 6361).

-marcel
## ... by: samuel

6 2 5 1 7 8 9 4 3

9 4 8 3 2 6 1 5 7

3 7 1 9 4 5 8 6 2

2 5 7 6 1 9 3 8 4

4 6 3 5 8 7 2 9 1

1 8 9 4 3 2 5 7 6

7 9 2 8 6 3 4 1 5

5 1 6 2 9 4 7 3 8

8 3 4 7 5 1 6 2 9

is that right?
## ... by: Strmckr

Jean-Claude Casari: answered via email.

a question for andrew if he reads this:

how come your solver never upgraded to include the

als-xy rule:

instead you are using mike barkers

Deathblosom which is also an als-xy rule but limited in its effectiveness through restrictions in its initial design.

## ... by: Jean-Claude

Very nice picture, strmckr, I have to buy colour pens to get there !

In order to let better understand your method, could you draw the equivalent picture for unsolvable # 27.

Many thanks,

Jean-Claude Casari

casarijc@hotmail.fr
## ... by: strmckr

ronk: posted a great pic of the logic set.

http://i41.tinypic.com/16kqmvd.jpg

after the BI BI pattern it solve using singles, 3 locked pairs 3 locked candidates and 1 skyscraper

I'm thinking the remote pairs is a bit excessive :P

## ... by: JC Van Hay

Typo in previous post (C1 -> C3). Thus :

2 very simple steps to solve the puzzle :

#1. Exocet pattern : see ttt's post in http://www.sudoku.org.uk/SudokuThread.asp?fid=4&sid=11320&p1=1&p2=17.

#2. Remote pairs : RP(35)C3B5 => +7r1c5; stte.
## ... by: JC Van Hay

2 very simple steps to solve the puzzle :

#1. Exocet pattern : see ttt's post in http://www.sudoku.org.uk/SudokuThread.asp?fid=4&sid=11320&p1=1&p2=17.

#2. Remote pairs : RP(35)C1B5 => +7r1c5; stte.
## ... by: Jean-Claude

I have no logical solution: there no bi-value cell.

Help !
## ... by: Nick the Geek

Wow! Immediate "Rooks!" (Run Out Of Known Strategies)! I'll give it a go today.