All files / lib/internal priority_queue.js

100% Statements 117/117
97.29% 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 11824x 24x 24x 24x 24x 24x 24x 24x 24x 24x 24x 24x 24x 24x 24x 24x 24x 24x 24x 24x 588x 588x 588x 588x 588x 588x 588x 588x 24x 24x 52411x 52411x 24x 24x 5462x 5462x 5462x 5462x 5462x 5462x 5462x 5462x 5462x 24x 24x 17728x 17728x 24x 24x 10083x 10083x 10083x 10083x 10083x 10083x 10083x 19575x 19575x 19575x 19575x 19575x 19575x 17311x 18353x 17311x 17311x 17311x 10083x 10083x 10083x 10083x 24x 24x 5463x 5463x 5463x 5463x 5463x 5463x 19793x 19793x 19793x 19223x 19223x 19265x 19223x 19223x 5463x 5463x 5463x 5463x 24x 24x 4162x 4162x 4162x 4162x 4162x 4162x 2691x 2691x 2690x 2690x 2691x 4162x 24x 24x 3582x 3582x 3582x 3582x 3577x 3577x 3577x 3577x 3582x 24x  
'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;
  }
};