Slightly adapted from a clever SQLite solution by Edzard Pasma and uses Peter Norvig's method. Requires a recent version of the SQLite3 DLL since it uses recursive CTEs (Common Table Expression).
Norvig's algorithm goes like this:
-- . from given Sudoku problem, generate an array with each cell of the
sudoku being a string with all remaining possibilites
-- . define as "neighbors" of a cell, all cells which must not have the
same piece as this cells, (there are 20 neighbo