SAT-based sudoku solver
This is a very simple solver that uses the Picosat library to do the hard work.
make
./doku < test/sudoku17.49151.txt
One notable thing about this program is that it runs much faster if
you add more constraints. There are three lines in main as follows:
all_diff_row(p);
all_diff_col(p);
all_diff_box(p);
If you comment out those lines, the program takes about 50 seconds to
solve the first 20 problems in test/sudoku17.49151.txt. With the
lines added, it takes under 0.01 seconds, and can run the whole set
of 49,151 problems in about 18s on my laptop.