flat-tree

A series of functions to map a binary tree to a list

npm install flat-tree

Usage

You can represent a binary tree in a simple flat list using the following structure

      3
  1       5
0   2   4   6  ...

This module exposes a series of functions to help you build and maintain this data structure

var tree = require('flat-tree')
var list = []

var i = tree.index(0, 0) // get array index for depth: 0, offset: 0
var j = tree.index(1, 0) // get array index for depth: 1, offset: 0

// use these indexes to store some data

list[i] = 'a'
list[j] = 'b'
list[tree.parent(i)] = 'parent of a and b'

API

`index = tree.index(depth, offset)`

Returns an array index for the tree element at the given depth and offset.

`parentIndex = tree.parent(index)`

Returns the index of the parent element in tree.

`siblingIndex = tree.sibling(index)`

Returns the index of this elements sibling.

`children = tree.children(index)`

Returns an array [leftChild, rightChild] with the indexes of this elements children. If this element does not have any children it returns null.

`range = tree.spans(index)`

Returns the range (inclusive) the tree root at index spans. For example tree.spans(3) would return [0, 6] (see the usage example).

`index = tree.leftSpan(index)`

Returns the left spanning in index in the tree index spans.

`index = tree.rightSpan(index)`

Returns the right spanning in index in the tree index spans.

`count = tree.count(index)`

Returns how many nodes (including parent nodes) a tree contains.

`count = tree.countLeaves(index)`

Returns how many nodes (excluding parent nodes) a tree contains.

`depth = tree.depth(index)`

Returns the depth of an element.

`offset = tree.offset(index, [depth])`

Returns the relative offset of an element.

`roots = tree.fullRoots(index)`

Returns a list of all the full roots (subtrees where all nodes have either 2 or 0 children) < index. For example fullRoots(8) returns [3] since the subtree rooted at 3 spans 0 -> 6 and the tree rooted at 7 has a child located at 9 which is >= 8.

`iterator = tree.iterator(index)`

Create a stateful tree iterator starting at a given index. The iterator exposes the following methods.

`index = iterator.next()`

Move the iterator the next item in the tree.

`index = iterator.prev()`

Move the iterator the prev item in the tree.

`iterator.seek(index)`

Move the iterator the this specific tree index.

`index = iterator.parent()`

Move the iterator to the current parent index.

`index = iterator.leftChild()`

Move the iterator to the current left child index.

`index = iterator.rightChild()`

Move the iterator to the current right child index.

`index = iterator.leftSpan()`

Move the iterator to the current left span index.

`index = iterator.rightSpan()`

Move the iterator to the current right span index.

`bool = iterator.isLeft()`

Is the iterator at a left sibling?

`bool = iterator.isRight()`

Is the iterator at a right sibling?

`index = iterator.sibling()`

Move the iterator to the current sibling.

`count = iterator.count()`

Returns how many nodes (including parent nodes) the current tree contains.

`count = iterator.countLeaves()`

Returns how many nodes (excluding parent nodes) the current tree contains.

License

MIT

Current Tags

1.9.0 ... latest (4 years ago)