Initial numbers give multiple solutions.
Hi. I decided to try playing some sudoku the other day, got quite a bit into and decided to play a few games on the 'hard' difficulty. Anyway, I got stuck, so I decided to make a guess and draw in successive numbers lightly to see if I could find a contradiction. Bafflingly, I didn't find a contradiction and got stuck again, so I made another guess. Anyway, I ended up finding a valid solution, checked it on the paper copy I was using and entered it into the program and it lit up green. Problem is, there were two valid ways of solving it. Worse still, I tried restarting the game and do an automatic solve, and it gave me yet another solution. This is bad, there must only be one valid solution compatible with the initial numbers in a game of sudoku. I took screenshots of the initial game numbers (top-left), the automatic solve (bottom-left) and my two solutions (right). The differences between my two solutions is very small, I've put red circles around the differences in the bottom-left grid.
Unfortunately these forums won't let me put an image in the post. Here's a direct link to it on photobucket: