I wanted to know if it was possible to continue when all well-known solving techniques are exhausted?
For example, a lot of "very hard" sudokus from http://www.printsudoku.com stick me, and even stick logical computer solvers like http://www.sudokusolver.co.uk/...
Let's look at Very hard Sudoku #67 from http://www.printsudoku.com...
- Code: Select all
Solution so far :
27- --- -68
--4 2-- 9--
6-- 8-5 ---
9-- -5- 63-
--- -2- ---
-18 -3- --4
--- 5-2 --9
--3 --7 1--
89- --- -76
Pencilmarks so far :
2.. 7.. 159 134 149 134 45. 6.. 8..
15. 8.. 4.. 2.. 7.. 6.. 9.. 15. 3..
6.. 3.. 19. 8.. 149 5.. 247 12. 27.
9.. 24. 27. 147 5.. 8.. 6.. 3.. 17.
3.. 45. 6.. 147 2.. 14. 8.. 9.. 157
57. 1.. 8.. 6.. 3.. 9.. 257 25. 4..
17. 6.. 17. 5.. 8.. 2.. 3.. 4.. 9..
4.. 25. 3.. 9.. 6.. 7.. 1.. 8.. 25.
8.. 9.. 25. 134 14. 134 25. 7.. 6..
The logical solver only uses just another technique like me and it removes number 5 from r6c7 with what you call X-Wing technique.
And then it makes a guess!!!
Would have it been possible to continue without making a guess?
Thank you for your help!
P.S. : Sorry if my English isn't really correct, I am French...