node-ds

A common data-structure and basic algorithm implemention in javascript

Table of Contents

• Quick Start
  • Installation
• Data Structures
  • Linear
    • Array
    • Linked List
    • Doubly Linked List
    • Linked Queue
    • Linked Stack
  • Trees
    • Binary Tree
      • Binary Search Tree
      • Self-balancing binary search tree
      • AVL Tree
      • Scapegoat Tree
      • Red-Black Tree
    • B-trees
      • B+ tree
      • 2-3 tree
      • 2-3-4 tree
    • Heap
      • Binary heap
      • Weak heap
      • Binomial heap
      • Fibonacci heap
  • Graph
  • Others
    • Node
    • DoublyNode
    • BinaryTreeNode
• Algorithms
  • Sorting Algorithms
    • Insertion-Sort
    • Merge-Sort
    • Quick-Sort
    • Heap-Sort
  • Statistics Algorithms
    • Grubbs
• Test
• Contributing to node-ds

Quick Start

Installation

Installation is done using the npm install command:

$ npm install node-ds

Data Structures

Linear

Array

Linked List

insertStart(val)

• val any

insertEnd(val)

• val any

deleteFirst()

Returns the deleted node.

deleteLast()

Returns the deleted node.

traverse(fn)

• fn Function

Apply fn to each node, and returns an array of elements returned by fn.

length

The number of nodes contained in the list.

head

Gets the first element of the LinkedList.

Doubly Linked List

Same with LinkedList

Linked Queue

Queue implemented by DoublyLinkedList

enqueueNode(node)

• node DoublyNode

Adds a node to the end of the Queue.

enqueue(val)

• val any

Adds an element to the end of the Queue.

dequeueNode()

Removes and returns the node at the beginning of the Queue.

dequeue()

Removes and returns the element at the beginning of the Queue.

traverse(fn)

• fn Function

Apply fn to each node, and returns an array of elements returned by fn.

peek()

Returns the element at the beginning of the Queue without removing it.

clear()

Removes all elements from the Queue.

length

The number of elements contained in the Queue

Linked Stack

Stack implemented by DoublyLinkedList

pushNode(node)

• node DoublyNode

push(val)

• val any

popNode()

Removes and returns the node at the top of the Stack.

pop()

Removes and returns the element at the top of the Stack.

peek()

Returns the element at the top of the Stack without removing it.

clear()

Removes all elements from the Stack.

length

The size of queue

Trees

Binary Tree

Unlike List, Queue, Stack and Hashtable, binary trees store data in a non-linear fashion and is a special kind of tree, on in which all nodes have at most two children, left and right.

*inOrder()

Inorder traversal starts by visiting the current node's left child, then the current node, and then its right child.

*preOrder()

Preorder traversal starts by visiting the current node, then its left child, and then its right child.

*postOrder()

Postorder traversal starts by visiting the current node's left child, then its right child, and finally the current node itself.

*levelOrder()

Levelorder traversal starts by visiting the current node and nodes in the same height, from left to right.

clear()

Remove _root reference in binary tree.

root

Get or set the root node of the binary tree

Binary Search Tree

A binary search tree is a special kind of binary tree, for node n , every descendant node's value in left subtree is less than the value of n, and every descendant nodes' value in the right subtree is greater than the value of n.

add(val)

• val any

Insert value according to the rule of BST.

delete(val)

• val any

has(val)

• val any

Return true or false if exist value.

Scapegoat Tree

A scapegoat tree is a self-balancing binary search tree. Instead of the small incremental rebalancing operations used by most balanced tree algorithms, scapegoat trees rarely but expensively choose a "scapegoat" and completely rebuild the subtree rooted at the scapegoat into a complete binary tree. Thus, scapegoat trees have O(n) worst-case update performance.

contructor(alpha = 0.667)

• alpha Number

α should be 0.5 < α < 1.A high α value results in fewer balances, making insertion quicker but lookups and deletions slower, and vice versa for a low α. Therefore in practical applications, an α can be chosen depending on how frequently these actions should be performed.

add(val)

• val any

delete(val)

• val any

has(val)

• val any

Return true or false if exist value.

Others

Node

• next Node
• val any

DoublyNode

• prev DoublyNode
• next DoublyNode
• val any

BinaryTreeNode

• left BinaryTreeNode
• right BinaryTreeNode
• val any

Algorithms

Sorting Algorithms

Sort the given array in ascending order, which is numerical order for number, alphabetic order for string. For array consisting of other data types, or if a customed order is prefered, a compare funtion must be specified. All sorting algorithms follow the same API. Check it out below.

• SortFamily
  • SortFamily.insertionSort(array[, compare[, lo, hi]]) or SortFamily.insertionSort(array[, lo, hi])
  • SortFamily.mergeSort(array[, compare[, lo, hi]]) or SortFamily.mergeSort(array[, lo, hi])
  • SortFamily.quickSort(array[, compare[, lo, hi]]) or SortFamily.quickSort(array[, lo, hi])
  • SortFamily.heapSort(array[, compare[, lo, hi]]) or SortFamily.heapSort(array[, lo, hi])
  • options:
    • array: array to sort, must be javascript Array object
    • compare: optional, a function(@return 1 or -1 or 0) telling in what order an element should be sorted. If compare(a, b) > 0, a will be placed after b, vice versa. If compare(a, b) = 0, the order of a and b will depend on the sorting algorithm. If compare is not specified, numbers will be sorted in numerical order, strings will be sorted in alphabetic order(according to gb2312 code point, if string cannot be encoded with gb2312, an error will be thrown)
    • lo: optional, default 0
    • hi: optional, default array.length - 1

Check some examples out below:

const SortFamily = require('node-ds/SortFamily.js');
const Random = require('node-ds/Random.js');

let a = [5,7,8,9,1,3,2,4,6];
function compare(a, b) {
    if (a > b) return -1;
    if (b > a) return 1;
    return 0;
}

SortFamily.insertionSort(a); // outputs [1, 2, 3, 4, 5, 6, 7, 8, 9]

SortFamily.insertionSort(a, compare); // outputs [9, 8, 7, 6, 5, 4, 3, 2, 1]

Random.shuffle(a); // say [6, 7, 9, 2, 3, 5, 1, 8, 4]
SortFamily.insertionSort(a, 3, 6); // outputs [6, 7, 9, 1, 2, 3, 5, 8, 4]

Random.shuffle(a); // say [6, 9, 3, 1, 4, 2, 8, 5, 7]
SortFamily.insertionSort(a, compare, 3, 6); // outputs [6, 9, 3, 8, 4, 2, 1, 5, 7]

Statistics Algorithms

Find out outliers from the given data array based on some basic mathematical calculation(average、stdev).

Grubbs

const Grubbs = require('node-ds/Grubbs.js');

let data = [7, 9, 2, 6, 3, 5, 7, 2, 4, 20];
let grubbs = new Grubbs(data);
grubbs.getOutliers();//outputs [9], means the number 20 is outlier

Test

Like most other packages, just run test suite and check code coverage by following commands:

$ npm test
$ npm run cover

Contributing to node-ds