Priority Queue

A priority queue is a data structure with these operations:

| Operation | Syntax (ts-priority-queue) | Description | | --------- | --- | ----------- | | Create | var queue = new PriorityQueue(); | Creates a priority queue | | Queue | queue.queue(value); | Inserts a new value in the queue | | Length | var length = queue.length; | Returns the number of elements in the queue | | Peek | var firstItem = queue.peek(); | Returns the smallest item in the queue and leaves the queue unchanged | | Dequeue | var firstItem = queue.dequeue(); | Returns the smallest item in the queue and removes it from the queue | | Clear | queue.clear(); | Removes all values from the queue |

You cannot access the data in any other way: you must dequeue or peek.

Provides an O(log n) approach to priority queue insertions and removals. I forked this from the CoffeeScript js-priority-queue library so that I could write it in TypeScript. I've removed the array- and BHeap-based strategies as they were not recommended for use anyway.

Installing

You can npm install ts-priority-queue

Then write code like this:

var queue = new PriorityQueue({ comparator: function(a, b) { return b - a; }});
queue.queue(5);
queue.queue(3);
queue.queue(2);
var lowest = queue.dequeue(); // returns 5

Options

How exactly will these elements be ordered? Let's use the comparator option. This is the argument we would pass to Array.prototype.sort:

var compareNumbers = function(a, b) { return a - b; };
var queue = new PriorityQueue({ comparator: compareNumbers });

You can also pass initial values, in any order. With lots of values, it's faster to load them all at once than one at a time.

var queue = new PriorityQueue({ comparator: compareNumbers, initialValues: [ 1, 2, 3 ] })

Complexity:

| Operation | Complexity | | --------- | ----------- | | Create | O(n lg n) | | Queue | O(lg n) | | Peek | O(1) | | Dequeue | O(lg n) |

License

Public Domain. Do with it what you will.