Alex Little

Yesterday I found a sudoku that my sudoku solver program couldn’t solve, so might try and find some time to update the algorithm (at some point). The reason my algorithm didn’t work was because there were (at least) 2 solutions to it, my algorithm looks for squares where only one number can fit (within either a single square, box, row or column), but with this sudoku you would get to a point where you had to decide which of two numbers to enter into a square – which one you entered didn’t matter because either would result in a valid solution. So looks like I need to make my algorithm cope with this somehow – haven’t thought yet exactly how I’ll do it though!

I’ve now finally got round to putting up the first version of my Sudoku solver program and online demo.

In some of my spare time at home, I’ve developed a sudoku solver program, which is nearly ready for me to make available. It uses jsp & servlet technology, and should run on tomcat or jboss. I’ve still got a few bits to finish off – the web interface is a bit basic at the moment, but so far the engine that actually solves the sudoku seems solid – well I’ve not managed to get it to fall over yet!! The actual engine isn’t particularly sophisticated, just keeps track of which numbers can go where and updates this everytime a new box is set to a particular number, it can then find which numbers can only go in a particular column, row, square,  or group of squares in order to solve the sudoku.
The web interface can:

• give you hints as to where the next numbers go
• show you the solution to the whole grid
• tell you whether or not the engine is able to solve the sudoku in it’s current state (if either it’s not solvable at all, or if not enough numbers are present to determine the solution)
• allow you to work on and solve 9×9 and 16×16 square sudokus – in fact the engine will cope with any size.

Anyway, hope to get this posted up in the next few days