The script on this page uses recursive backtracking to solve a sudoku puzzle.
For further information on recursion, see the recursion page in the Programming section.
There is also a Python
version of the Sudoku solver, which contains only the code required
to solve the problem and is thoroughly commented - it also shows multiple
solutions (where they exist) but isn't as easy to use.
Click to increase the number in a square and right-click to decrease it. Click Solve to find the solutions.