Download: Excel Sudoku solver aid (xls)
I have written an Excel spreadsheet that aids in the solution to sudoku problems. But rather than it just solve the problem directly and give the answer, it gives the reason for each number placement, and the user places the number in the grid themselves.
One of the benefits, is that it quickly shows if a sudoku is badly designed, i.e. unsolvable. That is because all sudoku puzzles should be stepwise solvable, and no trial and error is needed to select between possible solution routes.
The solver will show the following ‘moves’:
- Above each cell, it shows the possible numbers that can be placed, based on numbers placed in the same column, same row and same box.
- If any of the numbers 1 to 9 can be placed in a row (or column) directly (because they are uniquely above one cell in the row (or column).
- If any of the numbers 1 to 9 can be placed in a box directly (because they are uniquely above one cell in the box. This is shown below.
The last two rows, complete a test to ensure no numbers have been entered in error in the columns or boxes. The uniqueness of entries in the rows are check down the right hand side.