https://github.com/sraaphorst/sudoku_constexpr
Compile-time (constexpr) Sudoku board solver
https://github.com/sraaphorst/sudoku_constexpr
backtracking backtracking-algorithm compile-time constexpr cpp14 cpp17 sudoku sudoku-solver
Last synced: 2 months ago
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Compile-time (constexpr) Sudoku board solver
- Host: GitHub
- URL: https://github.com/sraaphorst/sudoku_constexpr
- Owner: sraaphorst
- Created: 2018-09-30T19:01:34.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2018-11-02T17:10:14.000Z (over 6 years ago)
- Last Synced: 2025-01-05T16:33:34.224Z (4 months ago)
- Topics: backtracking, backtracking-algorithm, compile-time, constexpr, cpp14, cpp17, sudoku, sudoku-solver
- Language: C++
- Size: 21.5 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
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Metadata Files:
- Readme: README.md
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README
# sudoku_constexpr
**Status:** Complete, verson 1.0.0.
This is a C++17 constexpr implementation of a Sudoku board solver, i.e. it solves Sudoku boards
at compile-time.
(It could be easily modified to run under C++14 if one eliminated the tuple binding.)
This uses a primitive backtracking approach, and is thus not meant for serious use,
but just as an exercise in exploring compile-time implementations of algorithms.
Efficient Sudoku solvers rely on more advanced techniques than naive backtracking, with one of
the most common techniques using Donald Knuth's "algorithm X" (generally called DLX or Dancing
Links).
I have an implementation of DLX and a Sudoku solver using DLX coded in C and Python.
The Python implementation can be found here on GitHub:
https://github.com/sraaphorst/dlxpy/blob/master/examples/sudoku.py
## Performance
Using what is considered an expert-level Sudoku board (as hard-coded in the implementation), on my MacBook, compilation takes approximately 3.5 minutes.
Using the well-known, extreme Sudoku from here (also hard-coded in the implementation):
https://www.telegraph.co.uk/news/science/science-news/9359579/Worlds-hardest-sudoku-can-you-crack-it.html
compilation takes slightly over 20 minutes on my MacBook.
## Compilation
This may not run under GCC due to GCC complaining that the call to solve is not actually `constexpr`. I suggest using clang instead.