7 releases

✓ Uses Rust 2018 edition

0.6.2 Jan 17, 2020
0.6.1 Nov 30, 2019
0.5.2 Aug 14, 2019
0.5.1 Jul 3, 2019
0.4.1 May 19, 2019

#67 in Algorithms

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65 downloads per month

MIT and LGPL-3.0


Ultimate nonograms solver written in Rust language.

Crates.io Build Status codecov

$ wget -qO- https://webpbn.com/export.cgi --post-data "id=32480&fmt=nin&go=1" | cargo run

Rust logo as nonogram image


  • solves binary (blank-and-white) and colored (<32 colors) nonograms;

  • supports wide variety of formats:

  • combines several solving methods to achieve speed for various puzzle types:

    • very simple puzzles are solved line-by-line (line + propagation);
    • if the puzzle cannot be solved, the probing phase begins, where assumptions are made about every unsolved cell following by the analysis of the impact they bring;
    • if the puzzle not solvable even here, the searching algorithms are enabled: by default backtracking is used that colors a cell, then another one, and go on, until the solution(s) is found. But there is another option (with sat feature): special SAT-solver, that uses the results of previous phases to more effectively explore the solution space.

By default the --features="args std_time logger ini" are enabled but you can disable almost anything to speed up and/or shrink the size of the binary.

Arguments parsing

To support command-line arguments, the args feature is enabled by default. You can disable it, but then you will not able to set solving timeout or maximum number of solutions to find. It also can be disabled when using the solver as a library in another projects, e.g.

Timeout (std_time)

By default you can provide the --timeout option to stop backtracking after reaching the specified time limit. You can disable this feature (std_time) and the timeout option will simply be ignored.

Logging support

To support pretty formatted logs the env_logger crate is enabled by default. The simplest way to view them is to provide environment variable RUST_LOG=nonogrid=<log_level>. For example, in the benchmarks script, the RUST_LOG=nonogrid=warn is used to inspect the intermediate results of solving. As always, you can disable the option by skipping the --features=logger while building.

TOML puzzles parsing support

My custom TOML-based format is supported by default via feature ini. It can be disabled when using the solver as a library in another projects, e.g.


By default, the backtracking algorithm used for solving hard puzzles. The feature sat allows to use the SAT solver for such a job. The most of hard puzzles are solved significantly faster with this option.

The latest benchmarks show that the SAT-solver is very effective for the hardest webpbn puzzles (actually, only two puzzles are found that solves longer than an hour: 25820 and 26520).

XML puzzles parsing support

The Jan Wolter's XML format supported via feature xml. You can enable it by building with the --features=xml.

Colored nonograms

You can enable the feature colors to allow to print colored nonograms with real terminal colors:

wget -qO- https://webpbn.com/export.cgi --post-data "fmt=olsak&go=1&id=2192" |
cargo run --no-default-features --features=colors

HTTP client

Solved puzzles can be automatically downloaded from the Internet with the reqwest library but it requires too many dependencies and increases compile time, so it's optional by default. Enable it as simple as:

cargo run --features=web,xml -- --webpbn 5933


By default, the solver and all the algorithms are single-threaded. To use the solver's structures in multi-threaded environment, provide the threaded feature. In essense, this feature replaces every occurence of Rc/RefCell with Arc/RwLock.

Probing tweaking

When the 'logical' solving (line/propagation) gets stuck, the probing phase starting which tries every variant for every unsolved cells. It does this by calculating the priority for each cell:

P = N + R + C,

where 0<=N<=4 - number of neighbours which are solved cells or puzzle edges.
For example, the cell which has all 4 heighboring cells solved, has N = 4.
The upper left cell of the puzzle without any neighbours solved, has N = 2,
since it has 2 edges of the puzzle.

0<=R<=1 - row solution rate, the ratio of solved cells in the row to total number of cells (width)
0<=C<=1 - column solution rate, the ratio of solved cells in the column to total number of cells (height)

By default every cell with P>=0 checked, but you can customize the threshold by specifying the LOW_PRIORITY environment variable.

For example, running

LOW_PRIORITY=1 nonogrid puzzles/6574.xml

can be solved 3 times faster than standard way, by skipping the probing of cells with P < 1.

Usage examples

Solve locally saved puzzles from https://webpbn.com (XML format)

cargo build --features="xml"

# solve puzzle https://webpbn.com/2992
wget 'https://webpbn.com/XMLpuz.cgi?id=2992' -O 2992.xml
target/debug/nonogrid 2992.xml

# with pipe
wget -qO- 'https://webpbn.com/XMLpuz.cgi?id=2992' | target/debug/nonogrid

Solve puzzles from https://webpbn.com (with embedded HTTP-client)

cargo build --features="web,xml"

# solve puzzle https://webpbn.com/5933
target/debug/nonogrid -w 5933

Solve locally saved puzzles from https://nonograms.org

cargo build

# solve puzzle https://webpbn.com/2992
wget -qO- 'https://www.nonograms.org/nonograms/i/2581' | grep 'var d=' > 2581.js
target/debug/nonogrid 2581.js

# with pipe
wget -qO- 'https://www.nonograms.org/nonograms/i/2581' | target/debug/nonogrid

Solve puzzles from https://nonograms.org (with embedded HTTP-client)

cargo build --features="web"

# solve puzzle https://www.nonograms.org/nonograms/i/13588
target/debug/nonogrid -o 13588

# solve puzzle https://www.nonograms.org/nonograms2/i/10270
target/debug/nonogrid -o 10270

Solve other formats

TOML format

cargo build

target/debug/nonogrid examples/hello.toml

Webpbn's exportable formats

wget -qO- https://webpbn.com/export.cgi --post-data "fmt=syro&go=1&id=2040" |
cargo run --no-default-features


See the INFO logs and unfold backtrace on panic

RUST_BACKTRACE=1 RUST_LOG=nonogrid=info cargo run -- examples/hello.toml


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