Deque

this is just a implementation of Python deques in JS. Deques are a generalization of stacks and queues (the name is pronounced “deck” and is short for “double-ended queue”).

Though list objects support similar operations, they are optimized for fast fixed-length operations and incur O(n) memory movement costs for pop(0) and insert(0, v) operations which change both the size and position of the underlying data representation.

Install

npm install dqs 

Usage

let dqueue = require('dqs')

 Methods

insert(x)

Add x to the right side of the deque.

all

Return all the objects in an Array.

clear()

Remove all elements from the deque leaving it with length 0.

count(x)

Count the number of deque elements equal to x.

pop()

Remove and return an element from the right side of the deque. If no elements are present, raises an IndexError.

popleft()

Remove and return an element from the left side of the deque. If no elements are present, raises an IndexError.

let dq = new DQueue([2,3,0,1])
let v1 = dq.popLeft()
let v2 = dq.popLeft()

console.log(v1, v2) // 2 3
console.log(dq.all()) // [0,1]

rotate(n=1)

Rotate the deque n steps to the right. If n is negative, rotate to the left.

let dqueue = new DQS([2,3,0,1])
dqueue.rotate(-2)
//[0,1,2,3]

When the deque is not empty, rotating one step to the right is equivalent to d.appendleft(d.pop()), and rotating one step to the left is equivalent to d.append(d.popleft()).