priority-queue-v2

Published at - https://www.npmjs.com/package/priority-queue-v2

Operations supported -

queue - add an element to the queue

dequeue - delete the max priority element from the queue

isEmpty - returns true/false

clear - clear the queue

delete - If we need to update the priority, delete that item and insert it in again

list - contents of heap

The Item stored in the queue should be class and a comparator should be provided.

By default, duplicate elements are not allowed.
To allow duplicates in the queue add the allowDuplicates argument to true.

let obj = new PriorityQueue(comparator, true)

Examples -

1. If values in a queue are strings, comparator will receive priorities as a and b in the example below

We need max priority element to be removed first.

let comparator = function (a, b) {

return a >= b ? false : true

}

An example would be - 
const PriorityQueue = require('../index.js').priorityQueue
let obj = new PriorityQueue(comparator)
obj.queue('c', 1)
obj.queue('b', 3)
obj.queue('a', 5)
console.log(obj.dequeue()) //'a'

2. If values in the queue is an object, comparator will receive the object and you need to compare priorities as seen below -

class Box {
  constructor(w, l) {
        this.w = w
        this.l = l
        this.area = w * l //this is priority
  }
  comparator(a, b) {
        return a.area >= b.area ? false : true
  }
}
    
    let obj = new PriorityQueue(Box.prototype.comparator)
    obj.queue(new Box(5, 5))
    obj.queue(new Box(2, 3))
    obj.queue(new Box(3, 3))
    obj.queue(new Box(9, 9))
    
    assert.deepEqual(obj.dequeue(), new Box(9, 9))
    assert.deepEqual(obj.dequeue(), new Box(5, 5))