Schroeppel, Richard wrote:
---- Sudoku: I ran across a moral dilemma in a Sudoku last night: Can I use the uniqueness of the solution to exclude some lines of argument?
It's a question of morals all right - I think it's a matter of preference. If you don't assume a unique solution, while deriving the solution you also *prove* that there is a unique solution. The dilemma also arises in other puzzles. Wei-Hua Huang wrote a post about it re Battleship: http://www.mountainvistasoft.com/t-uniq.htm Sometimes problems (e.g. Putnam problems) can be solved by a trick if you assume there is a solution. Huang gives a nice example. Most sudoku enthusiasts don't seem to mind assuming the uniqueness rule, judging by the hundreds, nay thousands, of forum posts on the various conclusions that can be drawn. Personally I don't like using it, but would use it if stuck. I don't find it as morally reprehensible as making an outright guess. Gary McGuire