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[], startPos?: number, endPos?: number) | void | Initialize priority queue with initial elements. enqueue(val: T) | void | Drop a element into the priority queue. enqueues(elements: T[], startIndex?: number, endIndex?: number) | void | Drop multiple elements into the priority queue. dequeue() | T|undefined | Popup the top element. splice(filter, newElements?: T[], startIndex?: number, endIndex?: number) | void | Remove existed elements which is not passed the filter, then enqueues the additional elements. replaceTop(newElement: T) | void | Replace top element with new one. (If the queue is empty, then the newElement will be enqueued.) 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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