The New Sudoku Players' Forum

[bbriscoe]

I've gotten this far, but I can't ever seem to finish a very hard puzzle without hints. What tricks do I need to find the next big number?



. . 2 | . . . | 4 8 .
. . 8 | 2 4 . | 1 . .
. . . | . 7 . | . . 2
------+-----+------
2 . . | 9 8 . | . 4 1
1 . . | 4 2 . | . . 9
4 . . | 1 5 7 | . . .
------+-----+------
5 . . | 7 6 . | . . 8
. . 2| 5 . 4 | 3 . .
. 1 7| . . . | . 5 4



I've gone thru and done pencil marks and found pairs like 3,6 in the middle square, and 3,4 in the 7th row columns 2 and 3.

What's next?

[Ruud]

What's next?

A good step would be to remove a 2 from either R1C3 or R8C3.

Without the 2 in R8C3 the puzzle solves easily with singles and locked candidates only.

Ruud.

[bbriscoe]

I'm sorry, I had it wrong: I had the 2 in row 1 in the wrong column.
This should be correct. Now what are locked candidates?

. 2 . | . . . | 4 8 .
. . 8 | 2 4 . | 1 . .
. . . | . 7 . | . . 2
------+-----+------
2 . . | 9 8 . | . 4 1
1 . . | 4 2 . | . . 9
4 . . | 1 5 7 | . . .
------+-----+------
5 . . | 7 6 . | . . 8
. . 2| 5 . 4 | 3 . .
. 1 7| . . . | . 5 4

[SarC]

Now what are locked candidates?

Check this page http://angusj.com/sudoku/hints.php

[Ruud]

After you've mastered the locked candidates, read on to learn about naked pairs and triples .
With those 2 techniques, you will be able to solve this one.

Ruud.