I like to play Sudoku at work I’m aware of a sidebar gadget on Vista that lets you play Sudoku. (Gotta be careful, my manager reads this. :)) One day when experimenting with this gadget (I was testing it, really…), I discovered a potential solution that, while technically correct, was counted as incorrect.
You see the incorrect values in red. You can go through the row / column / square checking or you can take my word for it – that solution is correct. However, the sidebar gadget seemed to think that this alternative, similar solution was the right one:
In fact, they’re both correct. Which brings up an interesting question to ponder: Under what circumstances are Sudoku solutions unique? When can multiple solutions exist?
Continuing on the train of deep Sudoku thinking, I noticed that the Sudoku games in this gadget don’t start off symmetrically (if you look at Sudoku puzzles in the books or newspaper, the starting values are symmetric along the diagonal). Is there something important about this symmetry? Is the symmetry at all correlated with unique solutions?
I call on some really smart math whiz (Eric) to solve this problem immediately.