go-sudoku is an entry for Go Challenge 8.

go-sudoku < input.txt

or, more interestingly:

go-sudoku -steps < input.txt

See example

1 _ 3 _ _ 6 _ 8 _
_ 5 _ _ 8 _ 1 2 _
7 _ 9 1 _ 3 _ 5 6
_ 3 _ _ 6 7 _ 9 _
5 _ 7 8 _ _ _ 3 _
8 _ 1 _ 3 _ 5 _ 7
_ 4 _ _ 7 8 _ 1 _
6 _ 8 _ _ 2 _ 4 _
_ 1 2 _ 4 5 _ 7 8

Run go-sudoku -help for a full list of optional arguments.

go-sudoku first attempts human strategy and ultimately falls back on a SAT solver.

The SAT solver takes advantage of some Sudoku characteristics to shorten execution time. It's rather good at determining unsolvable boards.

• http://www.sudokuwiki.org/Strategy_Families
• https://en.wikipedia.org/wiki/Simplex_algorithm
• http://www.nature.com/articles/srep00725#f3
• http://arxiv.org/ftp/arxiv/papers/0805/0805.0697.pdf
• Satisfiability Solvers: http://www.cs.cornell.edu/gomes/papers/satsolvers-kr-handbook.pdf
• http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-005-elements-of-software-construction-fall-2011/assignments/MIT6_005F11_ps4.pdf
• https://en.wikipedia.org/wiki/Conjunctive_normal_form
• https://en.wikipedia.org/wiki/DPLL_algorithm
• https://en.wikipedia.org/wiki/Backtracking
• https://en.wikipedia.org/wiki/Unit_propagation
• http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-005-elements-of-software-construction-fall-2011/lecture-notes/
• Puzzle Generation
• http://www.sudokuwiki.org/sudoku_creation_and_grading.pdf
• http://www.websudoku.com/faqs.php
• http://planetsudoku.com/how-to/sudoku-squirmbag.html
• http://www.sudoku-solutions.com/index.php?page=background
• https://gophers.slack.com/files/mem/F0DHMJBML/top95.txt
• http://www.websudoku.com/
• https://en.wikipedia.org/wiki/Exact_cover#Sudoku