# At what n, does a n^2xn^2 sudoku puzzle take too long to solve? [closed]

I'm creating a sudoku solver, and I'm wondering at what point, with a simple backtracking sudoku solving algorithm, does the result take way too long to compute? I'm thinking like more than 30 minutes? I'll probably try to implement some heuristics, but I want to know at what point should I not expect a solution within 30 minutes?

• This is not an answerable question in its current form, as the answer depends too much on the specific solver. Moreover, you are the right one to answer this: you have your code, you can get test cases, so why haven't you just tried it and see? Why are you asking here? On this site, we expect you to make a serious effort to answer your question on your own before asking here; in this case, that would include trying it experimentally. See the help center (upper-right part of the page) for more explanation of this site format and our expectations. – D.W. Apr 18 '14 at 19:45

Some sudoku puzzles of arbitrary size are easy to solve, for example if every number is given except for $1$ number (that's an extreme example, but the point is that different sudoku puzzles will take different amounts of time to be solved by a given solver). So it sounds like you want to know the worst-case running time for you solver, i.e. find the hardest puzzle for your solver. But we don't know how your solver works, and even if we did, figuring out the hardest puzzle for your solver for each $n$ would be an almost certainly impossible task. There are examples of "hard" sudoku puzzles on the web, but you shouldn't expect them to necessarily be the absolute hardest for your solver. Your question is basically impossible to answer unless you enumerate all sudoku puzzles for each $n$ that have a unique solution and try them all out, in increasing order of $n$ until you finally find a worst-case puzzle that takes more than $30$ minutes to run or whatever your time limit is for your solver.