&gt; in as optimal a fashion one can deterministically solve it in<p>I&#x27;m curious what you mean by this? Sudoku is mechanically solvable, but not all sudoku puzzles <i>feel</i> that way, to me.<p>Uh, I haven&#x27;t actually done sudoku in a long time, so let me talk about kakuro (<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Kakuro" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Kakuro</a>) instead. I think the feelings I have about them are similar.<p>So yes, I expect it would be fairly easy to write a backtracking kakuro solver. But the way I solve kakuro is very little like naive backtracking. I do things like - this row can only have numbers two to six, and this column can only have numbers five-plus, so this square is either five or six. But the row can only have one of those numbers, which means <i>this</i> square is two to four, and of those, four is the only number that fits in <i>this</i> column.<p>And getting a computer to implement that sort of algorithm would be challenging. (<a href="http:&#x2F;&#x2F;www.sudokuhints.com&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.sudokuhints.com&#x2F;</a> seems to do something like it for sudoku, to let it give you a number and tell you how you could have found that number yourself. But trying a fiendish puzzle, it&#x27;s not explaining itself very well.)<p>(Obviously, if you don&#x27;t enjoy sudoku, that&#x27;s fine. I&#x27;m not trying to convince you that you should. It just feels to me like the skills I use for sudoku, aren&#x27;t ones that I could trivially teach to a computer.)