http://www.brainbashers.com/sudoku.asp
It's not nightmare standard, but it is hard.
Code: Select all
.-----------------------.-----------------------.-----------------------.
|. . 3 |7 . 1 |8 . . |
|. . . |9 5 2 |. . . |
|1 . . |. 3 . |. . 7 |
:-----------------------+-----------------------+-----------------------:
|6 8 . |. . . |. 9 5 |
|. 7 2 |. . . |1 8 . |
|4 3 . |. . . |. 6 2 |
:-----------------------+-----------------------+-----------------------:
|2 . . |. 8 . |. . 9 |
|. . . |5 7 6 |. . . |
|. . 7 |2 . 4 |5 . . |
'-----------------------'-----------------------'-----------------------'
But what puzzles me is that the brainbusters site lists which techniques
it thinks you need to use to solve the puzzle. Forcing chains is not on
its list.
Here is its list:
Techniques Required:
Forced Moves
Pinned Squares
Locked Sets (x3)
Intersection Removal (x1)
Unique Rectangles (x2)
XY-Wing (x2)
But I cannot see this. I don't see any unique rectangles at all, and
if, as I suspect, it is considering c5r1, c9r1, c5r5, c9r5 a unique
rectangle, then it ought not to. The correct number just happens to
be the one that was filled in, but these values lie in 4 houses, not 2,
and so you cannot use uniqueness in this case.
Am I just missing something?
Laura