All files / lib/internal priority_queue.js

100% Statements 117/117
97.3% Branches 36/37
100% Functions 8/8
100% Lines 117/117

Press n or j to go to the next uncovered block, b, p or k for the previous block.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 11819x 19x 19x 19x 19x 19x 19x 19x 19x 19x 19x 19x 19x 19x 19x 19x 19x 19x 19x 19x 426x 426x 426x 426x 426x 426x 426x 426x 19x 19x 52411x 52411x 19x 19x 4335x 4335x 4335x 4335x 4335x 4335x 4335x 4335x 4335x 19x 19x 11894x 11894x 19x 19x 7788x 7788x 7788x 7788x 7788x 7788x 7788x 19123x 19123x 19123x 19123x 19123x 19123x 17213x 18255x 17213x 17213x 17213x 7788x 7788x 7788x 7788x 19x 19x 4336x 4336x 4336x 4336x 4336x 4336x 19332x 19332x 19332x 18857x 18857x 18899x 18857x 18857x 4336x 4336x 4336x 4336x 19x 19x 3484x 3484x 3484x 3484x 3484x 3484x 2651x 2651x 2650x 2650x 2651x 3484x 19x 19x 2906x 2906x 2906x 2906x 2901x 2901x 2901x 2901x 2906x 19x  
'use strict';
 
const {
  Array,
  Symbol,
} = primordials;
 
const kCompare = Symbol('compare');
const kHeap = Symbol('heap');
const kSetPosition = Symbol('setPosition');
const kSize = Symbol('size');
 
// The PriorityQueue is a basic implementation of a binary heap that accepts
// a custom sorting function via its constructor. This function is passed
// the two nodes to compare, similar to the native Array#sort. Crucially
// this enables priority queues that are based on a comparison of more than
// just a single criteria.
 
module.exports = class PriorityQueue {
  constructor(comparator, setPosition) {
    if (comparator !== undefined)
      this[kCompare] = comparator;
    if (setPosition !== undefined)
      this[kSetPosition] = setPosition;
 
    this[kHeap] = new Array(64);
    this[kSize] = 0;
  }
 
  [kCompare](a, b) {
    return a - b;
  }
 
  insert(value) {
    const heap = this[kHeap];
    const pos = ++this[kSize];
    heap[pos] = value;
 
    if (heap.length === pos)
      heap.length *= 2;
 
    this.percolateUp(pos);
  }
 
  peek() {
    return this[kHeap][1];
  }
 
  percolateDown(pos) {
    const compare = this[kCompare];
    const setPosition = this[kSetPosition];
    const heap = this[kHeap];
    const size = this[kSize];
    const item = heap[pos];
 
    while (pos * 2 <= size) {
      let childIndex = pos * 2 + 1;
      if (childIndex > size || compare(heap[pos * 2], heap[childIndex]) < 0)
        childIndex = pos * 2;
      const child = heap[childIndex];
      if (compare(item, child) <= 0)
        break;
      if (setPosition !== undefined)
        setPosition(child, pos);
      heap[pos] = child;
      pos = childIndex;
    }
    heap[pos] = item;
    if (setPosition !== undefined)
      setPosition(item, pos);
  }
 
  percolateUp(pos) {
    const heap = this[kHeap];
    const compare = this[kCompare];
    const setPosition = this[kSetPosition];
    const item = heap[pos];
 
    while (pos > 1) {
      const parent = heap[pos / 2 | 0];
      if (compare(parent, item) <= 0)
        break;
      heap[pos] = parent;
      if (setPosition !== undefined)
        setPosition(parent, pos);
      pos = pos / 2 | 0;
    }
    heap[pos] = item;
    if (setPosition !== undefined)
      setPosition(item, pos);
  }
 
  removeAt(pos) {
    const heap = this[kHeap];
    const size = --this[kSize];
    heap[pos] = heap[size + 1];
    heap[size + 1] = undefined;
 
    if (size > 0 && pos <= size) {
      if (pos > 1 && this[kCompare](heap[pos / 2 | 0], heap[pos]) > 0)
        this.percolateUp(pos);
      else
        this.percolateDown(pos);
    }
  }
 
  shift() {
    const heap = this[kHeap];
    const value = heap[1];
    if (value === undefined)
      return;
 
    this.removeAt(1);
 
    return value;
  }
};