A performant priority queue implementation using a Heap data structure.
npm install --save @datastructures-js/priority-queuePriorityQueue in this repo is implemented as two types: MinPriorityQueue which uses a MinHeap and considers an element with smaller priority number as higher in priority. And MaxPriorityQueue which uses a MaxHeap and cosiders an element with bigger priority number as higher in priority.
const { MinPriorityQueue, MaxPriorityQueue } = require('@datastructures-js/priority-queue');import {
MinPriorityQueue,
MaxPriorityQueue,
PriorityQueueOptions, // queue options interface
PriorityQueueItem // queue item interface
} from '@datastructures-js/priority-queue';The constructor accepts a callback to get the numeric priority from the queued element. If not passed, the constructor adds a default priority callback that returns the numeric value of the element itself.
// empty queue with default priority the element value itself.
const numbersQueue = new MinPriorityQueue();
// empty queue, will provide priority in .enqueue
const patientsQueue = new MinPriorityQueue();
// empty queue with priority returned from a prop of the queued object
const biddersQueue = new MaxPriorityQueue({ priority: (bid) => bid.value });const numbersQueue = new MinPriorityQueue<number>();
const patientsQueue = new MinPriorityQueue<string>();
interface Bid {
name: string;
value: number;
}
const biddersQueue = new MaxPriorityQueue<Bid>({
priority: (bid: Bid) => bid.value
});adds an element with a numeric priority to the queue. Priority is not required here if a priority callback has been provided in the constructor. If passed here with a constructor callback, it will override the callback.
| params | return | runtime |
|---|---|---|
|
element: T
priority: number |
MinPriorityQueue<T> | MaxPriorityQueue<T> | O(log(n)) |
// MinPriorityQueue Example, where priority is the number element itself
numbersQueue
.enqueue(10)
.enqueue(-7)
.enqueue(2)
.enqueue(-1)
.enqueue(-17)
.enqueue(33);
// MinPriorityQueue Example, where priority is the patient's turn
patientsQueue
.enqueue('patient y', 1) // highest priority
.enqueue('patient z', 3)
.enqueue('patient w', 4) // lowest priority
.enqueue('patient x', 2);
// MaxPriorityQueue Example, where priority is the bid's value.
biddersQueue
.enqueue({ name: 'bidder y', value: 1000 }) // lowest priority
.enqueue({ name: 'bidder w', value: 2500 })
.enqueue({ name: 'bidder z', value: 3500 }) // highest priority
.enqueue({ name: 'bidder x', value: 3000 });returns the element with highest priority in the queue.
| return | runtime |
|---|---|
| PriorityQueueItem<T> | O(1) |
console.log(numbersQueue.front()); // { priority: -17, element: -17 }
console.log(patientsQueue.front()); // { priority: 1, element: 'patient y' }
console.log(biddersQueue.front()); // { priority: 3500, element: { name: 'bidder z', value: 3500 } }returns an element with a lowest priority in the queue.
| return | runtime |
|---|---|
| PriorityQueueItem<T> | O(1) |
console.log(numbersQueue.back()); // { priority: 33, element: 33 }
patientsQueue.enqueue('patient m', 4); // lowest priority
patientsQueue.enqueue('patient c', 4); // lowest priority
console.log(patientsQueue.back()); // { priority: 4, element: 'patient c' }
biddersQueue.enqueue({ name: 'bidder m', value: 1000 }); // lowest priority
biddersQueue.enqueue({ name: 'bidder c', value: 1000 }); // lowest priority
console.log(biddersQueue.back()); // { priority: 1000, element: { name: 'bidder y', value: 1000 } }removes and returns the element with highest priority in the queue.
| return | runtime |
|---|---|
| PriorityQueueItem<T> | O(log(n)) |
console.log(numbersQueue.dequeue()); // { priority: -17, element: -17 }
console.log(numbersQueue.front()); // { priority: -7, element: -7 }
console.log(patientsQueue.dequeue()); // { priority: 1, element: 'patient y' }
console.log(patientsQueue.front()); // { priority: 2, element: 'patient x' }
console.log(biddersQueue.dequeue()); // { priority: 3500, element: { name: 'bidder z', value: 3500 } }
console.log(biddersQueue.front()); // { priority: 3000, element: { name: 'bidder x', value: 3000 } }checks if the queue is empty.
| return | runtime |
|---|---|
| boolean | O(1) |
console.log(numbersQueue.isEmpty()); // false
console.log(patientsQueue.isEmpty()); // false
console.log(biddersQueue.isEmpty()); // falsereturns the number of elements in the queue.
| return | runtime |
|---|---|
| number | O(1) |
console.log(numbersQueue.size()); // 5
console.log(patientsQueue.size()); // 5
console.log(biddersQueue.size()); // 5returns a sorted array of elements by their priorities from highest to lowest.
| return | runtime |
|---|---|
| PriorityQueueItem<T>[] | O(n*log(n)) |
console.log(numbersQueue.toArray());
/*
[
{ priority: -7, element: -7 },
{ priority: -1, element: -1 },
{ priority: 2, element: 2 },
{ priority: 10, element: 10 },
{ priority: 33, element: 33 }
]
*/
console.log(patientsQueue.toArray());
/*
[
{ priority: 2, element: 'patient x' },
{ priority: 3, element: 'patient z' },
{ priority: 4, element: 'patient c' },
{ priority: 4, element: 'patient w' },
{ priority: 4, element: 'patient m' }
]
*/
console.log(biddersQueue.toArray());
/*
[
{ priority: 3000, element: { name: 'bidder x', value: 3000 } },
{ priority: 2500, element: { name: 'bidder w', value: 2500 } },
{ priority: 1000, element: { name: 'bidder y', value: 1000 } },
{ priority: 1000, element: { name: 'bidder m', value: 1000 } },
{ priority: 1000, element: { name: 'bidder c', value: 1000 } }
]
*/clears all elements in the queue.
| runtime |
|---|
| O(1) |
numbersQueue.clear();
console.log(numbersQueue.size()); // 0
console.log(numbersQueue.front()); // null
console.log(numbersQueue.dequeue()); // null
patientsQueue.clear();
console.log(patientsQueue.size()); // 0
console.log(patientsQueue.front()); // null
console.log(patientsQueue.dequeue()); // null
biddersQueue.clear();
console.log(biddersQueue.size()); // 0
console.log(biddersQueue.front()); // null
console.log(biddersQueue.dequeue()); // nullgrunt build
The MIT License. Full License is here
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