SudoCue Users

A question for Ruud:

Are the Daily Nightmare puzzles always "valid" (in terms of the Wikipedia definition)? In other words, does each puzzle have only one unique solution?

You do not publish puzzles that have no solution, and you do not publish puzzles that have multiple solutions. Correct?

Thank you,

Keith

Hi Keith!

The answer is YES!

All the Sudokus published by me (not only here but also on my other websites) have been verified (if not created) by a DLX algorithm. This algorithm is also built into SudoCue, the Windows solver.

My Dutch sudoku friends know that I'm sort of a crusader against sites that publish non-solvable or multi-solution sudokus, so don't worry. You will never ever see them on my site.

As for your next question: Yes. you can use uniqueness test, BUG and other techniques that rely on the puzzle's uniqueness to solve it. You can even use Magic Cells, if you can find them (there are on average 2 in each Nightmare).

Currently I'm running a series that does not require uniqueness, but expect them from time to time amongst the Nightmares, upto the rare uniqueness tests 3 and 4.

If you do not like these methods, the Nightmares can (so far) always be solved by other means. For this, read the elaborate posts by your fellow puzzlers. I will not guarantee that this will always be the case....

Anyway, have fun solving these sudokus.

Ruud.