Generate a minesweeper board which doesn't need guessing
I am designing a Minesweeper-like game (with modified rules), and I want to prevent player from guessing. My goal is: The generated board is with few revealed squares, and player can solve the entire puzzle without any guessing.
Wikipedia mentioned:
Some implementations of Minesweeper will set up the board by never placing a mine on the first square revealed, or by arranging the board so that the solution does not require guessing.
However, I cannot figure out the algorithm.
Besides, in another StackOverflow question: Minesweeper solving algorithm
Improvement: Run the solver alongside the generator, making sure that the puzzle has a unique solution. This takes some cleverness, and isn't done in most variants.
I doubt if this really works. It's well-known solving minesweeper is NP-complete.
In summary, my questions are:
- How to generate a Minesweeper board which doesn't need any guessing?
- If we can, what's the concrete algorithm?
- Could we solve this problem in polynomial time deterministically? Is this problem NP-complete? How to prove it?
Answer
The implementation of Minesweeper in Simon Tatham's Portable Puzzle Collection is guessing-free. (It's also MIT licensed, so you're free to copy his implementation if you so desire.)