@algorithm.ts/priority-queue

Priority queue.

Usage no npm install needed!

<script type="module">
  import algorithmTsPriorityQueue from 'https://cdn.skypack.dev/@algorithm.ts/priority-queue';
</script>

README

@algorithm.ts/priority-queue


A typescript implementation of Priority Queue, the internal data structure is a max heap.

Priority Queue is a special queue structure, the first element of the queue always returns to the maximum value in the queue, and the amortized time complexity of the enqueue and dequeue operations are both $O(\log N)$.

Install

  • npm

    npm install --save @algorithm.ts/priority-queue

  • yarn

    yarn add @algorithm.ts/priority-queue

  • deno

    import { createPriorityQueue } from 'https://raw.githubusercontent.com/guanghechen/algorithm.ts/main/packages/priority-queue/src/index.ts'

Usage

  • IPriorityQueue

    Member Return Description
    init(elements?: T[]) void Initialize priority queue with initial elements.
    enqueue(val: T) void Drop a element into the priority queue.
    dequeue() T|undefined Popup the top element.
    top() T|undefined Get the top element.
    size() number Return the number of elements of the priority queue.
    isEmpty() boolean Check if the priority queue is empty.
    collect() T[] Return all of the elements of the priority queue.

  • createPriorityQueue

    export function createPriorityQueue<T>(
  cmp: (x: T, y: T) => -1 | 0 | 1 | number,
): IPriorityQueue<T>
    • createPriorityQueue<number>((x, y) => x - y): The top element has a maximum value.
    • createPriorityQueue<number>((x, y) => y - x): The top element has a minimum value.

Example

  • Basic

    import { createPriorityQueue } = '@algorithm.ts/priority-queue'

const Q = createPriorityQueue<number>((x, y) => x - y)

Q.enqueue(3)
Q.enqueue(7)
Q.enqueue(1)
Q.enqueue(-5)

Q.size()      // => 4
Q.isEmpty()   // => false

Q.dequeue()   // => 7
Q.dequeue()   // => 3
Q.top()       // => 1
Q.top()       // => 1
Q.dequeue()   // => 1
Q.top()       // => -5
Q.dequeue()   // => -5
Q.top()       // => undefined
Q.dequeue()   // => undefined

Q.isEmpty()   // => true

  • A solution for 剑指offer#63 https://www.nowcoder.com/practice/9be0172896bd43948f8a32fb954e1be1

    import { createPriorityQueue } from '@algorithm.ts/priority-queue'

const lowerQ = createPriorityQueue<number>((x, y) => x - y)
const upperQ = createPriorityQueue<number>((x, y) => y - x)

export function Insert(num: number): void {
  if (lowerQ.size() === upperQ.size()) {
    upperQ.enqueue(num)
    lowerQ.enqueue(upperQ.dequeue()!)
  } else {
    lowerQ.enqueue(num)
    upperQ.enqueue(lowerQ.dequeue()!)
  }
}

export function GetMedian(): number {
  return lowerQ.size() === upperQ.size()
    ? (lowerQ.top()! + upperQ.top()!) / 2
    : lowerQ.top()!
}

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