Sudoku solver

[Pekis]

The Sudoku solving algorithms are multiple (see Wikipedia) but the most fascinating for me is the one invented by Donald Knuth ("Algorithm X" (see Wikipedia)), with the Sudoku constraints fitted into an Exact cover problem (see Wikipedia).

After creating a big 729 (candidates) x 324 (constraints) sparse matrix and reducing it to a small data structure of linked nodes, that simple algorithm leads to an answer after a fraction of a second, much faster than a naive backtracking algorithm !

Do you think it could be programmable on an HP calc ?

Anyway, I made a simple and not recursive Android Java version (check the Solver class and the SatsNodesHandler class).

Best regards