Nikoli Puzzle Solver

Solver for over 100 types of Nikoli-style logic puzzles, including Sudoku, Slitherlink, Masyu, Nonograms, Skyscrapers, Light Up, Kakuro, and many more, conveniently deployed as a web app for easy use. Try it at https://util.in:8102.

The app hooks up to the Penpa UI to make it easy to input and view puzzles.

Features

• Supports over 100 puzzle types
• Supports unique solution checking
• Supports irregularly shaped grids and grids with holes (when appropriate for the puzzle type)
• Supports different tilings, such as hexagonal and triangular grids (when appropriate for the puzzle type)
• Easy for someone with programming experience to modify solvers for puzzle variants, or add new solvers

Instructions

• Go to https://util.in:8102.
• Input a puzzle, or choose a sample puzzle from the list on the bottom left. (You can also click Load to load any Penpa URL from the web.)
• In the dropdown menu on the bottom right, select the desired puzzle type/rules to solve with.
• Click "Solve". The grid will be automatically filled if a solution is found.

Development

One-time setup

To host the server yourself, you need Node.js. This was tested with Node.js v20.6.1.

Run the following:

git clone https://github.com/kevinychen/nikoli-puzzle-solver.git
cd nikoli-puzzle-solver
npm install
git submodule update --init

Running the server

To generate production assets and start the server, run:

npx webpack --mode production
node server.js

Then go to http://localhost:8080.

To run a development server, which will automatically refresh when the source code changes:

npx webpack serve --mode development

Running tests

Start the development server with npx webpack serve --mode development, then go to http://localhost:8080/test.html.

Adding a solver

• Create a new file in the solvers directory.
• Using the existing solvers as examples, define a solve function that takes a Z3 Context (to construct constraints) and a Puzzle (that contains the contents from the Penpa UI) as input.
• At the bottom of the file, add it to the solver registry with solverRegistry.push({...}).
  • You can construct the sample puzzle in Penpa, and click "Share" -> "Editing URL" to get the encoded puzzle.
• To fill in the sample answer, solve the sample puzzle in the UI and copy the puzzle answer string from the developer console logs.
• Run the tests to verify the new solver implementation and sample puzzle are correct.

Credits

This project was based on and inspired by the brilliant puzzle solver library Grilops. Thanks to puzz.link and similar sites for puzzle rules and sample puzzles.