Sudoku CSP

Solving Sudoku as a Constraint Satisfaction Problem using the AC-3 algorithm.

Results

Board: veryhard.txt

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

Solved

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