Greetings

I wrote a free solver/helper a few years ago called Jet Sudoku

Please feel free to download it here: http://manifestmaster.com/jetsudoku

I'm trying to update it to create new puzzles at random. This brings up

the issue of determining puzzle validity. As you know, a sudoku puzzle

is only valid if it is solvable and has only one solution.

One can prove that a puzzle is solvable by using traditional solving techniques,

but that does not prove that it cannot have more than one solution.

I had to come up with my own algorithm which I believe works but I'd like to

hear feedback from other programmers. Here's what Jet Sudoku does now:

Step 1: Solve the puzzle using brute force only, starting from r1c1 to r9c9

moving left to right.

Step 2: Solve the puzzle again using brute force only but starting from r9c9 to r1c1

moving right to left.

Compare the two solutions. If they're identical then I believe that the puzzle only

has one solution.

But I wonder if this is good enough.

I've considered using brute force two more times going down columns instead of across

rows, then doing it backwards.

I would appreciate any thoughts or feedback.