By Peter Nederlof, http://www.xs4all.nl/~peterned/.
Credits and thanks to Frank Verbruggen and Arnoud Berendsen.
This is a rule based sudoku solver. Basically it applies a certain rule, and then changes its approach based on the effect (solving or affecting any cells) of the rule that was applied. The script uses the following rules in a - currently hardcoded - strategy. Rows, columns and 3x3 squares are referred to as a "selection" for brevity:
Eliminating options from a selection when a number has been concluded is not a strategy rule. This simply happens everytime only 1 option remains for a certain cell, and can cascade all the way to the last cell. A future version will have a dropdown box in which you can select the strategy (order of rules) that is applied. Note that while I've succesfully tested this script with several evil sudokus from websudoku.com, I do not claim that this solver is capable of solving any solvable sudoku. In fact, the built in limit described in rule #2 and the current strategy might very well cause it to fail every now and then.