> I can copy values with values.copy() which is simple and efficient. If I implemented a possibility as a Python set or list I would need to use copy.deepcopy(v

> I can copy values with values.copy() which is simple and efficient. If I implemented a possibility as a Python set or list I would need to use copy.deepcopy(values), which is less efficient. The array deepcopy isn't too bad, at least when writing code, it compressed into a neat slice [:] I wrote a hinter[2] which was more fun than the actual solver too, because it shows the "minimum remaining values" as a colour coded chart. [1] - http://notmysock.org/code/sudoku/solver.py http://notmysock.org/code/sudoku/solver.py [2] - http://notmysock.org/code/sudoku/ http://notmysock.org/code/sudoku/