js-priority-queue/src/PriorityQueue/ArrayStrategy.coffee

Priority queue data structures

binarySearchForIndexReversed = (array, value, comparator) ->
  low = 0
  high = array.length
  while low < high
    mid = (low + high) >>> 1
    if comparator(array[mid], value) >= 0 # >=, instead of the usual <
      low = mid + 1
    else
      high = mid
  low

# Maintains a sorted Array. The running-time is bad in theory, but in
# practice Array operations are small ... assuming there isn't much data.
#
# The Array is stored from last entry to first: we assume queue() will be
# the same speed either way, but this way dequeue() is O(1) instead of O(n).
module.exports = class ArrayStrategy
  constructor: (@options) ->
    @comparator = @options.comparator
    @data = (@options.initialValues?.slice(0) || [])
    @data.sort(@comparator).reverse()

  queue: (value) ->
    pos = binarySearchForIndexReversed(@data, value, @comparator)
    @data.splice(pos, 0, value)
    undefined

  dequeue: ->
    @data.pop()

  peek: ->
    @data[@data.length - 1]

  clear: ->
    @data.length = 0
    undefined