## very very hard

Advanced methods and approaches for solving Sudoku puzzles

### very very hard

8.. ... 6..
.29 67. .1.
... .14 .5.

6.. 391 5.2
.51 ... 9..
9.2 ..6 ...

.6. 43. ...
.9. .87 16.
..7 ... ..3
cujka

Posts: 4
Joined: 17 September 2005

Have a look at R9C4 - you can make some eliminations. Then there's a hidden pair in block 1.

There's a few straightforward eliminations to get to this stage

Code: Select all
`81 [45]  [259]  [25]  [235] 6 [23479]  [479]  [45] 2967 [358]  [348] 1 [48]  [37]  [37] 6 [289] 14 [28] 5 [89] 6 [478]  [48] 3915 [478] 2 [37] 51 [278]  [24]  [28] 9 [3478] 69 [3478] 2 [578]  [45] 6 [3478]  [3478] 116 [58] 43 [259]  [278]  [2789]  [5789]  [245] 93 [25] 8716 [45]  [245]  [48] 716 [259]  [248]  [2489] 3`

Then there's a nice x-wing in rows 2 and 9.

stuartn
stuartn

Posts: 211
Joined: 18 June 2005

According to the solver at http://www.angusj.com/sudoku/
this puzzle has 6 solutions.
r.e.s.

Posts: 337
Joined: 31 August 2005

Ahaaa! - but I'm only looking for ONE of them!

let's not start this again......

stuartn
stuartn

Posts: 211
Joined: 18 June 2005

### one of the solutions...

814 523 679
529 678 314
736 914 258

678 391 542
351 742 986
942 856 731

165 439 827
493 287 165
287 165 493
jdevor

Posts: 3
Joined: 19 September 2005

### ... and the other five solutions

815 923 647
429 675 318
376 814 259

684 391 572
751 248 936
932 756 481

168 432 795
293 587 164
547 169 823

---------

815 923 647
429 675 318
376 814 259

684 391 572
751 248 936
932 756 481

168 439 725
293 587 164
547 162 893

---------

815 923 647
429 675 318
736 814 259

674 391 582
351 248 976
982 756 431

168 432 795
293 587 164
547 169 823

---------

815 923 647
429 675 318
736 814 259

674 391 582
351 248 976
982 756 431

168 439 725
293 587 164
547 162 893

---------

814 952 637
529 673 814
736 814 259

648 391 572
351 728 946
972 546 381

165 439 728
493 287 165
287 165 493
jdevor

Posts: 3
Joined: 19 September 2005