# Vanilla Priority Queue

A javascript implementation of a priority queue backed by a binary heap.

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- <a href="#Installation">Installation</a>
- <a href="#Usage">Usage</a>
- <a href="#API">API</a>

<a name="Installation"></a>
# Installation

```npm i vanilla-priority-queue --save```

<a name="Usage"></a>
# Usage

```

const {  MinPriorityQueue, MaxPriorityQueue } = require('vanilla-priority-queue');

let minPriorityQueue = new MinPriorityQueue();
/*
    The insert operation takes an item and it's priority.
    The item argument can be anything.
    The priority argument must be provided as an integer value.
*/
minPriorityQueue.insert(3, 3);
minPriorityQueue.insert(10, 10);
minPriorityQueue.peek() // returns 3
minPriorityQueue.remove() // returns 3
minPriorityQueue.remove() // returns 10
minPriorityQueue.isEmpty() // returns true


let maxPriorityQueue = new MaxPriorityQueue();
maxPriorityQueue.insert(3, 3);
maxPriorityQueue.insert(10, 10);
maxPriorityQueue.peek() // returns 10
maxPriorityQueue.remove() // returns 10
maxPriorityQueue.remove() // returns 3
maxPriorityQueue.isEmpty() // returns true

```

<a name="API"></a>
# API

Both the ```MaxPriorityQueue``` and ```MinPriorityQueue``` expose the following functions:

* **peek()**

Returns the highest priority item in the queue in constant time. For a ```MaxPriorityQueue``` this is the max element. For a ```MinPriorityQueue``` this is the min element.

* **insert(item, priority)**

The insert operation takes an ```item``` and it's ```priority``` and inserts the following object into the queue:

``` 
{
    item: item, 
    priority: priority
} 
```

The ```item``` argument can be anything.
The ```priority``` argument must be provided as an integer.

The operation completes in ```O(lg n)``` time.

* **remove()**

Removes the highest priority item in the queue in ```O(lg n)``` time. For a ```MaxPriorityQueue``` this is the max element. For a ```MinPriorityQueue``` this is the min element. 

* **isEmpty()**

Returns a boolean value indicating whether the queue is empty or not.

* **length()**

Returns the length of the queue.

* **getHeap()**

Returns an array representation of the binary heap backing the priority queue. Note this contains a dummy ```null``` element at index ```0```.