Is a fast implementation of the Dancing Links Algorithm applied to Sudoku. This is a rust rewrite of a Sudoku solver that I wrote a while back. Stripped off some mediocre features and made some improvements including

• Compacted the data structure with 16 bit cache-friendly pointers
• Removed some unnecessary fields.
• Smaller, neater and safer code. (Thanks to Rust!)
• About 30% faster. Solves all 50000 hardest puzzles collection in 1.9s on my laptop.

Write the Sudoku as a string of 81 characters and pass it to Stdin of qss. Example usage:

# compile
$ cargo build --release
$ cd target/release

# solve a puzzle
$ echo "000000010400000000020000000000050407008000300001090000300400200050100000000806000" | qss
  693784512487512936125963874932651487568247391741398625319475268856129743274836159

# solve puzzles from a file
$ qss < file.txt

# benchmarking
$ time cargo run --release < file.txt > /dev/null