Two implementations of binary search tree: basic and AVL (a kind of self-balancing binmary search tree). I wrote this module primarily to store indexes for NeDB (a javascript dependency-less database).
Package name is binary-search-tree.
npm install binary-search-tree --save
make testThe 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.
var BinarySearchTree = require('binary-search-tree').BinarySearchTree
, AVLTree = require('binary-search-tree').AVLTree // Same API as BinarySearchTree
// Creating a binary search tree
var 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 four 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.
var bst = new BinarySearchTree({ unique: true });
bst.insert(10, 'hello');
bst.insert(10, 'world'); // Will throw an error// 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
function 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
var bst = new BinarySearchTree({ compareKeys: compareKeys });
bst.insert({ age: 23 }, 'Mark');
bst.insert({ age: 47 }, 'Franck');// 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
function checkValueEquality (a, b) {
return a.length === b.length;
}
var bst = new BinarySearchTree({ checkValueEquality: checkValueEquality });
bst.insert(10, 'hello');
bst.insert(10, 'world');
bst.insert(10, 'howdoyoudo');
bst.delete(10, 'abcde');
bst.search(10); // Returns ['howdoyoudo']ONLY IMPLEMENTED WITH AVL !
// Each time a node's parent changes, the provided function will be called
var avl = new AVLTree({ notifyChanges: function(child, parent) {
console.log(parent.key+' is now parent of '+child.key);
});
// it works during insertions...
avl.insert(15, 'some data for key 15');
avl.insert(12, 'something else');
avl.insert(18, 'hello');
// and deletions
avl.delete(15);
avl.delete(18, 'world');(The MIT License)
Copyright (c) 2013 Louis Chatriot <[email protected]>
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