## Very Hard puzzle is stomping me

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### Very Hard puzzle is stomping me

I got this one on a daily sudoku web site. (2005-08-13)
When i got stuck, i programmed it on simple sudoku in order to get a better view, and when i was stuck again, i used the "hint"... but it answered, no hint available.... which never happened before.

Can this one be solved with logic only... i had to revert to trial and error with the x-wing 4's in order to solve it... which is cheating basically.

Hope someone can help !

Here's the text file from Simple Sudoku:
*-----------*
|1.8|4..|5..|
|...|..7|..2|
|...|...|...|
|---+---+---|
|.2.|.9.|..7|
|.6.|.5.|.89|
|9..|.1.|.4.|
|---+---+---|
|...|...|...|
|5..|6..|...|
|..4|..3|9.8|
*-----------*

E75007
E57007
E23006
E05006
E65001
E56001
E21002
E22002
E23002
E59004
E68004
E09004
E18004
E60002
E69002
E12003
E21003
Titouenne

Posts: 1
Joined: 13 September 2005

Titouenne wrote:Can this one be solved with logic only... i had to revert to trial and error with the x-wing 4's in order to solve it... which is cheating basically.
This is a difficult grid. I could only identify one double implication chain that removed a 5 in r3c3. It doesn't help at all.
This one may be solvable by triple implicatin chain or advanced colouring methods.

Angus, a 7 link turbot chain - case 4 is hidden in 5s of this grid.
Jeff

Posts: 708
Joined: 01 August 2005

Jeff wrote:Angus, a 7 link turbot chain - case 4 is hidden in 5s of this grid.

Tip for those wondering ...
If pink cell is 5 then exclude 5 from selected cell.
If amber cell is 5 then bright green cells must not be 5 so blue cells must be 5 so exclude 5 from selected cell.
angusj

Posts: 306
Joined: 12 June 2005

angusj wrote:
Tip for those wondering ...
If pink cell is 5 then exclude 5 from selected cell.
If amber cell is 5 then bright green cells must not be 5 so blue cells must be 5 so exclude 5 from selected cell.

Errr....
That's not so much of a tip for those of us who are colour-blind...
roger888

Posts: 19
Joined: 27 June 2005