The SuDoKu Challange

Let's spell it out: Our SudoKu puzzles are challanging! At many other Internet sites, there are puzzles that have a strait forward solution. Puzzles that can be solved by repeetingly picking out the one and only legal move at every time instant. Our (dumb but time-saving) SudoKu-Assistant would in-fact solve thoose puzzles in a split second! On the other hand, our puzzles requires the player to think several steps a head!

Our sudoku puzzles can be created in the following difficulties:

1, Easy
2, Puzzle for beginners
3, Nice and fun sudoku
4, Fun for non beginners
5, Difficult/interesting sudoku
6, Very difficult, experts only
6+, not recommended

We have found that some puzzles that we rate as "easy" are rated "very hard" in some news-papers. Those papers seam to use an oversimplified rating method based on the number of sudoku cells that are known when the game begins. When our program examines a sudoku it will check how difficult it is to solve it by a person who are looking for the well known solving clues (i.e. how advanced tricks one must use).

Our puzzles are computer aided designs! There is an intricate three-step-algorithm that designs them. Here is how it works:

A so called back-tracking algorithm fills in the 9x9-board with 81 figures which are as random as possible without violating anyone of the three SudoKu-rules (i.e., every row, column, and 3x3-region must contain exactly one figure of each kind). The result of this algorithm is the solution to a puzzle, but we still need to find the puzzle!

Next, another type of algorithm determines the subset of the board that we should disclose to the player! The result should be a puzzle that has exactly one solution, no more and no less. There are very many such puzzles and the algorithm will therefore output a set of representative puzzles, all of them having the solution found in step 1.

Among all puzzles found in step 2 we now need to pinpoint the most interesting one! This is done by a third algorithm that can simulate the human solving process and evaluate, by a heuristic formulae, the pleasure of solving a puzzle.

To sum up: In step 1, a solutions is found. Step two produces several puzzles that has that solution. Finally, in step 3, the most faschinating puzzle is pinpointed by a heuristic algorithm. And that puzzle is for you to solve!

svensk sudoku