KenKen solver in Rust

This is a solver for KenKen puzzles, which are similar to Sudoku, but have cages of varying sizes whose cells must fulfill mathematical operations.

The solver employs a combined strategy of first reducing the candidates for each cage, and each cell in a cage, and then searching the solution using backtracking. Combined with Rust this makes it pretty fast.

Input files

There are several example puzzles in examples. The input format should be pretty obvious. Here is a small example:

abbc
a2cc
ddef
4def

a: 1-
b: 3-
c: 36*
d: 7+
e: 2/
f: 2/

The first part is a description of the cages (the puzzle size is taken from the first line). Each cage has a corresponding character - numbers are reserved for single-cell constant cages. In the second part, each cage is mapped to its arithmetic rule.

Puzzles are accepted up to size 15x15.

Building and running

Build and run using cargo run --release -- puzzle.ken [...]. This is the output for the above example puzzle:

Puzzle              Solution
┏━━━┳━━━┯━━━┳━━━┓   ┏━━━┳━━━┯━━━┳━━━┓
┃1- ┃3- │   ┃36×┃   ┃ 2 ┃ 4 │ 1 ┃ 3 ┃
┠───╊━━━╈━━━╃───┨   ┠───╊━━━╈━━━╃───┨
┃   ┃ 2 ┃   │   ┃   ┃ 1 ┃ 2 ┃ 3 │ 4 ┃
┣━━━╇━━━╋━━━╈━━━┫   ┣━━━╇━━━╋━━━╈━━━┫
┃7+ │   ┃2÷ ┃2÷ ┃   ┃ 3 │ 1 ┃ 4 ┃ 2 ┃
┣━━━╅───╂───╂───┨   ┣━━━╅───╂───╂───┨
┃ 4 ┃   ┃   ┃   ┃   ┃ 4 ┃ 3 ┃ 2 ┃ 1 ┃
┗━━━┻━━━┻━━━┻━━━┛   ┗━━━┻━━━┻━━━┻━━━┛
examples/test4.ken          8 steps     0.0985 ms

When multiple input files are given on the command line, the squares are not printed, only the filename, number of backtracking steps and timing.