exact cover in Python

an implementation of Donald Knuth's Dancing Links algorithm in pure Python

Usage

pip install exact_cover_py

from exact_cover_py import exact_covers

problem = np.array([
        [1, 0, 0, 1, 0, 0, 1],
        [1, 0, 0, 1, 0, 0, 0],  # <--
        [0, 0, 0, 1, 1, 0, 1],
        [0, 0, 1, 0, 1, 1, 0],  # <--
        [0, 1, 1, 0, 0, 0, 1],
        [0, 1, 1, 0, 0, 1, 1],  # <--
        [0, 1, 0, 0, 0, 0, 1],
   ])

# exact_covers returns a generator of solutions

# one solution
print(next(exact_covers(problem)))
[1, 5, 3]

# all solutions
print(list(exact_covers(problem)))
[[1, 5, 3]]

# number of solutions
def mylen(iterable):
    return sum(map(lambda x: 1, iterable))

print(mylen(exact_covers(problem)))
2

Development

# build and install locally with tests dependencies
pip install -e .[tests]

pytest

Building and publishing

# deps
pip install build hatchling twine

# build
python -m build

# publish
twine upload dist/*