Uses graph to solve sudoku puzzles

sudoku.txt sourced from https://github.com/dimitri/sudoku/blob/master/sudoku.txt

and

https://abcnews.go.com/blogs/headlines/2012/06/can-you-solve-the-hardest-ever-sudoku

To run:

python sudoku.py

Results will show in solutions.txt