avl_tree
provides an implementation of an AVL Tree,
a selfbalancing binary searchtree.
It's basically a port from an implementation in Java by Justin Wheterell.
This implementation includes two custom features usually not present in AVL trees:

The methods
add
,remove
, orcontains
not only accept a value to be added, removed, or tested, but optionally also a compare function to be used in this very invocation only. This comes in handy, if a more efficient compare function can be used in a specific invocation. Example: the dynamically changing search tree of intersecting line segments in the BentleyOttmanAlgorithm. 
The tree can (optionally) store multiple values which are equal with respect to the tree ordering, but not identical with respect to Darts
identical()
function. One application is again the implementation of the Ystructure in the BentleyOttmanAlgorithm, where multiple overlapping line segments can be handled as equivalence class of line segments stored in one tree node.
Examples
A balanced tree of ints
// create a tree, and use some methods, use the standard
// int.compareTo function for ordering
var tree = new AvlTree<int>();
tree.addAll([0,1,2]);
print(tree.inorder.toList()); // > [0,1,2]
tree.remove(2);
print(tree.inorder.toList()); // > [0,1]
print(tree.contains(0)); // true
Reverse lexicographic order
Creates a balanced tree of strings, ordered in reverse lexicographic order.
// a balanced tree of strings, ordered in reverse lexicographical
// order
var order = (String s1, String s2) => s2.compareTo(s1);
var tree = new AvlTree<String>(compare: order);
tree.addAll(["aaa", "zzz"]);
print(tree.inorder.toList); // ["zzz", "aaa"]
A tree of strings with equivalence classes
Creates a tree of strings. The order is lexicographic with respect to the lowercase version of the strings. Strings which are equal modulo case are in the same equivalence class.
lowerCaseCompare(s,t) => s.toLowerCase().compareTo(t.toLowerCase());
var tree = new AvlTree<String>(compare:lowerCaseCompare,
withEquivalenceClasses: true);
tree.addAll(["aaa", "zzz", "AAA"]);
print(tree.smallest); // > ["aaa", "AAA"]
API documentation
Depend on it
avl_tree
is available from pub.dartlang.org. Add
dependencies:
avl_tree: "^0.1.1"
to your pubspec.yaml
.
See version history.
Status
License
avl_tree
is licensed under the Apache 2.0 license, see files LICENSE and NOTICE.