A Suduko Solver written in python for the Forrst Code Challenge.

Original Code Challenge

• Python 2.7

sudoku.py [-h] [-v] [-p] [--checkvalidity] [-i] filename

filename            name of file to load for sudoku puzzle

-h, --help          show this help message and exit  
-v, --verbose       produce detailed output
-p, --prettyoutput  print a nicely formatted output
--checkvalidity     check validity after solving. shouldn't be needed
-i, --interactive   go through the algorithm with pauses step by step

Note: you probably want to use the -p option to produce more readable output.

815493762
362875149
479261853
694357218
123984675
758126934
581732496
246519387
937648521

-------------
|815|493|762|
|362|875|149|
|479|261|853|
|-----------|
|694|357|218|
|123|984|675|
|758|126|934|
|-----------|
|581|732|496|
|246|519|387|
|937|648|521|
-------------

1. Use basic sudoku rules to produce possible values for board
2. If there are spaces that must contain a value based on the possible values, fill them.
3. Repeat from step 1 as long as new values are being filled.
4. If board is still unsolved, begin backtracking algorithm.
5. Start by choosing easiest square to solve (least possible solutions).
6. Choose a solution and create a new board instance, build it's possible values list (but without filling) and continue backtracking on that board.
7. Continue steps 4-6 recursively
8. Return solution or no possible solution.