container-avltreelist

container-avltreelist

AvlTreeList implementation in Javascript

It's a tree and a list at the same time.

To manage a pool of sorted elements. Complexity in O(log2(n)) for addition and removal. Plus, complexity in O(1) in the best case for repositioning an element after updating its sorting property. This container is best used for managing a list of element sorted when the values of the ordering properties change slowly over time.

List of methods and their time complexity

Method	Time Complexity
add	O(log2(n))
removeByReference	O(log2(n))
getCount	O(1)
popSmallest	O(log2(n))
popGreatest	O(log2(n))
getSmallestAbove	O(log2(n))
getGreatestBelow	O(log2(n))
forEach	O(n * p)
forEachReverse	O(n * p)
toArray	O(n)
clear	O(n)
reposition	best case in O(1), worst case in O(n)

Where:

• n is the number of elements in the tree
• p is the complexity of the process function.
• m is the number of elements that compare similarly to the given element

API usage

To instantiate a new tree:

// In this example, myTree will hold elements sorted by zIndex
function myComparisonFunction(a, b) {
	return a.zIndex - b.zIndex;
}

var myTree = new AvlTree(myComparisonFunction);

To add an element:

var myObjectReference = myTree.add(myObject); // O(log2(n))

To remove an element:

myTree.removeByReference(myObjectReference); // O(log2(n))

To apply a treatment on all the elements in sorted ordered:

myTree.forEach(function (object) {
	console.log(object);
});

To apply a treatment on all the elements in opposite sorted ordered:

myTree.forEachReverse(function (object) {
	console.log(object);
});

To get the smallest element greater or equal to a given object:

var myObjectAbove = myTree.getSmallestAbove({ zIndex: 4 }); // O(log2(n))

To get the greatest element smaller or equal to a given object:

var myObjectBelow = myTree.getGreatestBelow({ zIndex: 4 }); // O(log2(n))

To convert into an array:

var myArray = myTree.toArray(); // O(n)

To get the number of elements in the tree:

var nbElements = myTree.length;

To reposition an element whose sorting property changed:

var mTreey = new AvlTree(myComparisonFunction, 'avlTreeListReference'); // Setting the name of the property on which objects will keep their references
myObject.zIndex = 9;
myObject.avlTreeListReference = myTree.add(myObject);
myObject.zIndex = 10; // Sorting property (here zIndex) of element changed
myTree.reposition(myObject); // Repositioning object with respect to new sorting property value, will use the property name defined when constructing the tree, i.e 'avlTreeListReference'

Note 1: reposition method is in O(1) in the best case, and O(n) in worst case, depending on how much the value of sorting property changed.

Note 2: It is important to attach the object reference on the _avlTreeListReference property of the object.