82 lines
1.7 KiB
Markdown
82 lines
1.7 KiB
Markdown
# priority-queue
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functional, data oriented priority queue that doesn't suck
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There are many priority queue implementations on the web, but I couldn't find any that meet these critera:
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* **does not allocate memory at run time**
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* has tests
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* is functional, data oriented
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* is tiny! (~150 lines of code)
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* is a pure ES module
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So here we are!
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## Usage
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```javascript
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import PQ from 'priority-queue'
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// create a new priority queue that can hold a maximum of 20,000 items.
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// by default max length is 1000
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const MAX_LENGTH = 20000
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const obj = PQ.create(MAX_LENGTH)
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// insert a few items
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PQ.queue(obj, 'e', 1)
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PQ.queue(obj, 'f', 9)
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PQ.queue(obj, 'g', 4)
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// get the highest priority item out of the queue
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console.log(PQ.dequeue(obj)) // 'f'
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console.log(PQ.dequeue(obj)) // 'g'
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console.log(PQ.dequeue(obj)) // 'e'
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// when the queue is empty it'll return undefined on dequeue
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console.log(PQ.dequeue(obj)) // undefined
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```
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## API
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* `queue` - add an element to the queue
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* `dequeue` - delete the max priority element from the queue
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* `isEmpty` - returns true/false
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* `clear` - clear the queue
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* `delete` - If we need to update the priority, delete that item and insert it in again
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* `list` - contents of heap
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### Using classes/objects
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```javascript
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class Box {
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constructor(w, l) {
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this.w = w
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this.l = l
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this.area = w * l // this is priority
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}
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}
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const obj = PQ.create()
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const a = new Box(5, 5)
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const b = new Box(9, 9)
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const c = new Box(2, 3)
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const d = new Box(3, 3)
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PQ.queue(obj, a, a.area)
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PQ.queue(obj, c, c.area)
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PQ.queue(obj, d, d.area)
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PQ.queue(obj, b, b.area)
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assert.deepEqual(PQ.dequeue(obj), b)
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assert.deepEqual(PQ.dequeue(obj), a)
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```
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