# BK-tree

A BK-tree is a metric tree suggested by Walter Austin Burkhard and Robert M. Keller[1] specifically adapted to discrete metric spaces. For simplicity, let us consider integer discrete metric ${\displaystyle d(x,y)}$. Then, BK-tree is defined in the following way. An arbitrary element a is selected as root node. The root node may have zero or more subtrees. The k-th subtree is recursively built of all elements b such that ${\displaystyle d(a,b)=k}$. BK-trees can be used for approximate string matching in a dictionary [2].