Gudoku

A Sudoku solver written in Groovy.

About

This solver employs a pretty naive solving algorithm but should be able to solve all valid Sudokus. It uses a backtracking strategy coupled with picking cells that only have one candidate value in between backtracking calls.

If you find any Sudoku that cannot be solved by this program please open an issue on Github.

Command Line Interface

Usage

gudoku [options] <Sudoku>

Sudoku

A string containing the values of the cells from top left to bottom right. Anything other than 1..9 is interpreted as empty. Gudoku uses the convention of representing empty cells as "." but you can use any character you want. You can even mix and match different characters.

Gudoku will reject Sudokus containing collisions with an error message stating where the first collision occurred:

$ gudoku 11
Error: Specified seed contains a collision at position 2.

Examples

gudoku ""
gudoku .
gudoku 800000000003600000070090200050007000000045700000100030001000068008500010090000400
gudoku 8..........36......7..9.2...5...7.......457.....1...3...1....68..85...1..9....4..
gudoku 8..........36......7..9.2...5...7.......457.....1...3...1....68..85...1..9....4
gudoku 8----------36------7--9-2---5---7-------457-----1---3---1----68--85---1--9----4
gudoku 8__.....((-36._.((-7(-9-2((-5((-7_._.((-457..((-1((-3((-1.((-68(-85((-1(-9.((-4

The last 5 examples all represent the same Sudoku while the first 2 are empty. Notice:

• you need to use "" or at least one character to represent an empty Sudoku
• you can leave out empty cells at the end of the Sudoku

Options

--empty <char>

$ gudoku --pretty-print --empty - .
Read Sudoku:

- - - | - - - | - - -
- - - | - - - | - - -
- - - | - - - | - - -
------+-------+------
- - - | - - - | - - -
- - - | - - - | - - -
- - - | - - - | - - -
------+-------+------
- - - | - - - | - - -
- - - | - - - | - - -
- - - | - - - | - - -


Solving...


1 2 3 | 4 5 6 | 7 8 9
4 5 6 | 7 8 9 | 1 2 3
7 8 9 | 1 2 3 | 4 5 6
------+-------+------
2 1 4 | 3 6 5 | 8 9 7
3 6 5 | 8 9 7 | 2 1 4
8 9 7 | 2 1 4 | 3 6 5
------+-------+------
5 3 1 | 6 4 2 | 9 7 8
6 4 2 | 9 7 8 | 5 3 1
9 7 8 | 5 3 1 | 6 4 2

Set the character that represents an empty cell in the output. This option only makes sense in conjunction with -p, --pretty-print as the output does not contain empty cells otherwise. Notice:

• if you provide a string only the first character is used

-h, --help

gudoku -h
gudoku --help

Print a help message explaining how to use Gudoku.

-p, --pretty-print

gudoku -p .
gudoku --pretty-print .

Print the output in a human readable form.

File Expansion

This program supports argument file expansion via @:

gudoku @options.txt @sudoku.txt