The BK-Tree, which allows fast querying of "close" matches, such as Hamming distance (number of bits different). http://blog.notdot.net/2007/4/Damn-Cool-Algorit

The BK-Tree, which allows fast querying of "close" matches, such as Hamming distance (number of bits different). http://blog.notdot.net/2007/4/Damn-Cool-Algorithms-Part-1-BK-Trees http://blog.notdot.net/2007/4/Damn-Cool-Algorithms-Part-1-BK... I wrote a Python library implementing them a number of years ago: https://github.com/benhoyt/pybktree https://github.com/benhoyt/pybktree