@seald-io/binary-search-tree

Binary search trees for Node.js

This module is a fork of node-binary-search-tree written by Louis Chatriot for storing indexes in nedb.

Since the original maintainer doesn't support these packages anymore, we forked them (here is nedb) and maintain them for the needs of Seald.

Two implementations of binary search tree: basic and AVL (a kind of self-balancing binmary search tree).

Installation and tests

Package name is @seald-io/binary-search-tree.

npm install @seald-io/binary-search-tree

If you want to run the tests, you'll have to clone the repository:

git clone https://github.com/seald/node-binary-search-tree
npm install
npm test

Usage

The API mainly provides 3 functions: insert, search and delete. If you do not create a unique-type binary search tree, you can store multiple pieces of data for the same key. Doing so with a unique-type BST will result in an error being thrown. Data is always returned as an array, and you can delete all data relating to a given key, or just one piece of data.

Values inserted can be anything except undefined.

const BinarySearchTree = require('binary-search-tree').BinarySearchTree
const AVLTree = require('binary-search-tree').AVLTree   // Same API as BinarySearchTree

// Creating a binary search tree
const bst = new BinarySearchTree()

// Inserting some data
bst.insert(15, 'some data for key 15')
bst.insert(12, 'something else')
bst.insert(18, 'hello')

// You can insert multiple pieces of data for the same key
// if your tree doesn't enforce a unique constraint
bst.insert(18, 'world')

// Retrieving data (always returned as an array of all data stored for this key)
bst.search(15)   // Equal to ['some data for key 15']
bst.search(18)   // Equal to ['hello', 'world']
bst.search(1)    // Equal to []

// Search between bounds with a MongoDB-like query
// Data is returned in key order
// Note the difference between $lt (less than) and $gte (less than OR EQUAL)
bst.betweenBounds({ $lt: 18, $gte: 12 })   // Equal to ['something else', 'some data for key 15']

// Deleting all the data relating to a key
bst.delete(15)   // bst.search(15) will now give []
bst.delete(18, 'world')   // bst.search(18) will now give ['hello']

There are three optional parameters you can pass the BST constructor, allowing you to enforce a key-uniqueness constraint, use a custom function to compare keys and use a custom function to check whether values are equal. These parameters are all passed in an object.

Uniqueness

const bst = new BinarySearchTree({ unique: true });
bst.insert(10, 'hello');
bst.insert(10, 'world');   // Will throw an error

Custom key comparison

// Custom key comparison function
// It needs to return a negative number if a is less than b,
// a positive number if a is greater than b
// and 0 if they are equal
// If none is provided, the default one can compare numbers, dates and strings
// which are the most common usecases
const compareKeys = (a, b) => {
  if (a.age < b.age) return -1
  if (a.age > b.age) return 1

  return 0
}

// Now we can use objects with an 'age' property as keys
const bst = new BinarySearchTree({ compareKeys })
bst.insert({ age: 23 }, 'Mark')
bst.insert({ age: 47 }, 'Franck')

Custom value checking

// Custom value equality checking function used when we try to just delete one piece of data
// Returns true if a and b are considered the same, false otherwise
// The default function is able to compare numbers and strings
const checkValueEquality = (a, b) => a.length === b.length

var bst = new BinarySearchTree({ checkValueEquality })
bst.insert(10, 'hello')
bst.insert(10, 'world')
bst.insert(10, 'howdoyoudo')

bst.delete(10, 'abcde')
bst.search(10)   // Returns ['howdoyoudo']

License

The package is released under the MIT License as the original package.

See LICENSE.md.