A good place to start when you want to write your own Sudoku program is the Sudoku Programmers forum.
Testing Sudoku Programs
- Test Cases — a set of formal tests for Sudoku software
General N2 by N2 Sudokus
This wiki specializes on the standard 9 by 9 Sudoku, but we can generalize this puzzle game into a N2 by N2 one, where every row, every column, and every N by N box must contain each of the digits 1 to N2. The generalized Sudoku is known to be NP-complete, which means that it is very unlikely to have an efficient algorithm that can solve any N2 by N2 Sudoku exactly, with efficient meaning running time polynomial in N.
- Takayuki Yato and Takahiro Seta. Complexity and completeness of finding another solution and its application to puzzles. IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, E86-A(5):1052–1060, May 2003.