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Revision as of 22:51, 19 June 2015

Binary search tree
Simple Binary Search tree

General Information

Abstract data structure: Sorted sequence

Implementation invariant:

  1. There is a tree item type with three components:
    1. key is of generic type [math]\displaystyle{ \mathcal{K} }[/math],
    2. left and right of type "pointer to tree item of type [math]\displaystyle{ \mathcal{K} }[/math]."
  2. An object of the binary search tree type contains a pointer root of type "pointer to tree item of type [math]\displaystyle{ \mathcal{K} }[/math]."
  3. The pointer root points to a well-formed binary search tree. In accordance with the definition of directed trees, "well-formed" means that, for any node, there is exactly one path from the root to that node.

Remark

  • Besides the methods of sorted sequences, binary search trees in the implementation chosen here have a private method Binary Search Tree:Remove node, which receives a pointer [math]\displaystyle{ p }[/math] to a binary search tree node and removes it (possibly by removing another node and overwriting the key to be removed with the key of the other node. Prerequisite: [math]\displaystyle{ p }[/math].left [math]\displaystyle{ \neq }[/math]void.
  • There are variants on binary search trees, such as AVL trees and red-black-trees, for which the height of the tree is guaranteed to be in [math]\displaystyle{ O(\log{n}) }[/math] at any time (because the additional operations to maintain logarithmic height are linear in the height of the tree as well).
  • The mathematical concept behind this data structure is described in the section on binary search trees of page Directed Tree.