As many other pages around the internet, this one proposes a sudoku solver. But instead of strategy or constraints resolving, it proposes another approach to solve faster the sudoku. Its resolution is based on linear programmation. It is then very efficient, its only drawback resides in the fact that it cannot print intermediate steps.
The linear solver is lp_solve, a really great Mixed Integer Programming (MIP) solver distributed under LGPL License.
The page describing the linear method to resolve the sudoku is available with through this link.