Strategies for Number Puzzles of all kinds
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Wednesday 12-Dec-2018

... by: Hendrik Monard

In the result obtained after ROOKS (run out of known strategies in Andrew's logical solver), resetting the 'forbidden' candidates I2(6) I2(7) and E8(7) will lead to the solution of #325 in a logical solver.

Wednesday 12-Dec-2018

... by: Neil

Hi Rick,

I am a pen and paper solver, and have also developed a large Excel spreadsheet to help me solve the more difficult puzzles. I would suggest that you concentrate on reliably solving all the XY and XYZ Wings, before you move on to triples (more common than swordfish) and then swordfish.

Best regards


Monday 10-Dec-2018

... by: Rick in New Orleans

Thanks BobW.
That goldmine will keep me happy for a long time.

Monday 10-Dec-2018

... by: Tokay

Sorry two guesses:

Row Col Val
0 6 4
3 2 3

Monday 10-Dec-2018

... by: Tokay

3 gueses:

Row Col Val
0 0 3
4 0 2
2 0 4

Saturday 8-Dec-2018

... by: BobW

The software on this page doesn't allow me to include a link, but if you do a search for "enjoysudoku" you should get some hits for a fairly active forum that has a section devoted to software.

Saturday 8-Dec-2018

... by: Rick in New Orleans

Please excuse me if this comment is not appropriate to this space, but I don't imagine there are many pencil and paper solvers here. In past weeks I have seen posts by several programmers discussing their logic solvers. I am also working on a logic solver in excel with vba, and I would love to find a forum for logic solver programmers to discuss approaches to programming the more advanced techniques. I have X-wings done and my XY and XYZ wings find some but not all. I think Swordfish is probably next, then maybe back to triples. I also have a t&e routine for the puzzles here. Thanks.

Saturday 8-Dec-2018

... by: Frans Goosens

With trial and error

Combination A3=234 and D4=129

A3=2 D4=1 No solution, Fixed

Combination 2-digits cells

B4=2 Wrong, Undo calculation
B4=5 Wrong, Undo calculation

All reset to initial position

A3=2 D4=2 No solution, Fixed

Combination 2-digits cells

B4=1 No solution, Undo calculation
B4=5 Wrong, Undo calculation
B4=1 No solution, Fixed
A6=3 Wrong, Undo calculation
A6=9 ( A7=4 ) Solved,

080 700 000-------------182 759 436
690 000 800-------------694 132 875
005 008 090-------------375 648 291

500 006 080-------------543 296 187
000 400 300-------------726 481 359
008 070 002-------------918 573 642

050 000 010-------------257 864 913
000 300 700-------------469 315 728
001 020 004-------------831 927 564

Total solving time is : 116 sec.
Number of steps is : 11523

Saturday 8-Dec-2018

... by: BobW

182 759 436
694 132 875
375 648 291

543 296 187
726 481 359
918 573 642

257 864 913
469 315 728
831 927 564

Final Cell Values by Solve Order:

Initial (Clue) Values:
A2=8, A4=7, B1=6, B2=9, B7=8, C3=5, C6=8, C8=9, D1=5, D6=6, D8=8, E4=4, E7=3, F3=8, F5=7, F9=2, G2=5, G8=1, H4=3, H7=7, J3=1, J5=2, J9=4
E5=8, *J8=6, G9=3, H9=8, *J7=5, H8=2, G7=9, *J6=7, G6=4, J2=3, G5=6, J1=8, J4=9, G4=8, C4=6, D4=2, *D7=1, *D5=9, D9=7, E8=5, F6=3, F8=4, A8=3, B6=2, B8=7, C9=1, D2=4, D3=3, E6=1, F1=9, F4=5, F7=6, H1=4, H2=6, H3=9, H6=5, A6=9, B3=4, B4=1, B9=5, E9=9, F2=1, H5=1, A3=2, A7=4, A9=6, B5=3, C2=7, C5=4, C7=2, E2=2, G3=7, A1=1, A5=5, C1=3, E1=7, E3=6, G1=2
* Asterisk indicates trial & error assignment used when all logic strategies have been exhausted.

Deepest recursion: 10
Total steps including dead branches: 6987
Total patterns searched including dead branches: 1201
Total patterns found including dead branches: 30720
Total patterns found resulting in candidate elimination including dead branches: 790
Unlimited depth search Backdoor values: J8=6 J7=5 J6=7 D7=1 D5=9

Total solution time: 1.942 seconds

Minimal backdoor: A3=2 E1=7

No single cell backdoor found.


Each week a new 'unsolvable' will be published and the previous will be accessible here from this archive section. If you like very tough puzzles, these are for you.
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