by tso » Thu Feb 02, 2006 8:00 pm
The question has no meaning without defining your terms. The rating of "evil" has no agreed upon meaning -- we've all come across puzzles that were nearly trivial that were rated "evil" as well has very tough once rated "easy".
Things get only worse when you say "multiple solution" puzzle. A puzzle can be presented as having exactly 2 (or N) solutions -- the puzzle could be either trivial or as hard as the hardest puzzle ever seen. Mutiple solution puzzle of this type do have added difficulties: You can't use Unique Rectangles or BUG, you might have to make multiple copies of the grid, etc. You're basically solving two (or N) separate puzzles.
Then there are puzzles that *look* like multiple solution puzzles but aren't. "What is the number in the central cell?" might have one answer -- the answer the puzzle construtor is looking for -- though the Sudoku might have any number of solutions.
Then there are puzzles that are simply broken, posed as having a unique solution, but actually having dozens or hundreds. A puzzle like this is no better than one that has *no* solution. It is neither hard nor easy. It is impossible.