Brute force Sudoku solver written in C in 2005
It takes a single argument: the content of the cells in Western writing order (top to bottom, left to right). Unknowns are zeroes. It will return all possible solutions (if any).
$ make
$ ./sudoku 043080250600000000000001094900004070000608000010200003820500000000000005034090710
1 4 3 9 8 6 2 5 7
6 7 9 4 2 5 3 8 1
2 8 5 7 3 1 6 9 4
9 6 2 3 5 4 1 7 8
3 5 7 6 1 8 9 4 2
4 1 8 2 7 9 5 6 3
8 2 1 5 6 7 4 3 9
7 9 6 1 4 3 8 2 5
5 3 4 8 9 2 7 1 6