How do writers create a sudoku puzzle?

Zloar: How do writers create a sudoku puzzle?
What is the process for making a sudoku puzzle?

Are they reverse engineered, or is there some mathmatical process?

Answers and Views:

Answer by sillytillywillyandhannili
To create a Sudoku puzzle, writers will fill out the puzzle randomly, but correctly. Then, they erase most of the numbers, but leave enough for you, the player, the fill it out.

Answer by roynburton
That’s a tricky question. The usual process nowadays is for the creator to use a computer. Working in columns left to right, or rows top to bottom, the program fills the first randomly, then the next and so on, keeping the rule of not re-using a digit already used in the rows (or columns) so the 2nd column (or row) has only 8 digits to choose from for each cell. It will select for the top (or left) cell, then move down (or right) with fewer and fewer digits available as they are used in the column (or row).

Once filled out, the computer then removes “X number” of digits to make an easy puzzle, more for a harder one and so on for as hard as one wishes to make them.

GOOD creators now solve each puzzle to ensure there is only one solution for the puzzle after however many digits are removed. There is no elegant way currently used for this: the computer simply uses blunt force to start with the puzzle as it would be published and solving. If it finds only one solution, the puzzle is ready for publication and the beginning display and answer display is saved for publication. At this point, the effort the computer went through to “prove” the solution may modify what category it is put into. Might be, for instance, that an easy looking puzzle with many starting digits is actually a beast to solve.

If in that step, it is found that no umabiguous solution is possible (for instance, maybe it resolves to four cells at the end that could be 7, 1, 2, 5 or they could be 1, 5, 7, 2 which means two solutions exist and people will feel cheated), then the computer will usually loop back and put one more numbered cell into the starting puzzle and try again.

Blunt force, blunt force and more good blunt force. Nothing elegant really, except a step with a check to ensure they are not producing reflections of puzzles because no publisher wants to pay for that when they can do the reflections themselves! (A reflection is a puzzle in which the cells are rotated by 90, 180, or 270 degrees — so that the left column might now be the top row and so on.)