When you first crack open a new sudoku puzzle, do you look at the rows or columns first? Or do you work in blocks? What’s your strategy?
When you first crack open a new sudoku puzzle, do you look at the rows or columns first? Or do you work in blocks? What’s your strategy?
For each number, I mark all cells where I know I can’t put it.
If one block, column or row has only one possible cell where a number can be, I put it there and then update all cells where I now know I can’t put it anymore.
This algorithm probably isn’t the fastest, but it’s easy to do manually and it has the advantage that you don’t need to backtrack.