A simple sudoku solver that uses backtracking to solve any puzzle regardless of difficulty. Numpy optional.
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sudoku
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README.md
sudoku.py
sudoku_1.py

README.md

SudokuSolver

A simple Sudoku solver that uses backtracking to solve any puzzle regardless of difficulty. Implemented in both Python 3 and Processing (java).

Introduction

This is just a quick and dirty implementation of the backtracking algorithm for Sudoku solving. This uses Numpy for nicer array manipulation, but that's not necessary, it just made development quicker.

Features

Solves sudoku puzzles of any difficulty, either while describing each step in the process (if you use the first script) or silently (if you use the second script). It's barebones, designed to be a simple understandable implementation, rather than anything too fancy. It will provide a solution to any valid puzzle you give it, even if the puzzle has multiple possible answers.

The processing version will illustrate the steps that it uses to solve the problem on a sudoku grid as it solves it.

Animation illustrating the computational steps made in solving a puzzle

Installation & Usage

Clone the repo, and install Python (and Numpy), or, to use the processing version just open the sketch in processing and run it.

Edit one of the scripts and type in a puzzle at the top, using 0's as blank spaces. For example:

(6, 0, 0, 0, 0, 0, 0, 5, 1),
(0, 0, 0, 3, 0, 0, 9, 0, 0),
(0, 0, 8, 0, 0, 0, 0, 0, 0),
(0, 4, 0, 7, 0, 0, 5, 0, 0),
(0, 0, 0, 0, 9, 0, 8, 0, 0),
(0, 0, 1, 8, 5, 0, 0, 3, 7),
(5, 0, 2, 6, 0 ,0, 0, 0, 4),
(3, 0, 0, 0, 0, 7, 0, 2, 9),
(0, 0, 4, 0, 0, 0, 0, 0, 0)

Save the script and run it; it will print the puzzle and then return the solution:

C:\...\SudokuSolver>python sudoku_1.py

[[6 0 0 0 0 0 0 5 1]
 [0 0 0 3 0 0 9 0 0]
 [0 0 8 0 0 0 0 0 0]
 [0 4 0 7 0 0 5 0 0]
 [0 0 0 0 9 0 8 0 0]
 [0 0 1 8 5 0 0 3 7]
 [5 0 2 6 0 0 0 0 4]
 [3 0 0 0 0 7 0 2 9]
 [0 0 4 0 0 0 0 0 0]]

 Processing...

[[6 3 9 2 8 4 7 5 1]
 [2 1 7 3 6 5 9 4 8]
 [4 5 8 1 7 9 2 6 3]
 [8 4 3 7 2 1 5 9 6]
 [7 6 5 4 9 3 8 1 2]
 [9 2 1 8 5 6 4 3 7]
 [5 9 2 6 1 8 3 7 4]
 [3 8 6 5 4 7 1 2 9]
 [1 7 4 9 3 2 6 8 5]]

C:\...\SudokuSolver>

Contributing

Feel free to contribute as you wish, I'll accept all pull and merge requests if they're decent.

License

See LICENSE for details of the GNU GPL v3.0 license that this software falls under.