Class: PriorityQueue

Inherits:
Object
  • Object
show all
Defined in:
lib/priority_queue.rb

Overview

Priority Queue Reference: github.com/python/cpython/blob/main/Lib/heapq.py

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(array = [], &comp) ⇒ PriorityQueue

By default, the priority queue returns the maximum element first. If a block is given, the priority between the elements is determined with it. For example, the following block is given, the priority queue returns the minimum element first. ‘PriorityQueue.new { |x, y| x < y }`

A heap is an array for which a <= a and a <= a for all k, counting elements from 0.



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# File 'lib/priority_queue.rb', line 10

def initialize(array = [], &comp)
  @heap = array
  @comp = comp || proc { |x, y| x > y }
  heapify
end

Instance Attribute Details

#heap ⇒ Object (readonly) Also known as: to_a

Returns the value of attribute heap.



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# File 'lib/priority_queue.rb', line 28

def heap
  @heap
end

Class Method Details

.[](*array, &comp) ⇒ Object 



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# File 'lib/priority_queue.rb', line 24

def self.[](*array, &comp)
  new(array, &comp)
end

.max(array) ⇒ Object 



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# File 'lib/priority_queue.rb', line 16

def self.max(array)
  new(array)
end

.min(array) ⇒ Object 



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# File 'lib/priority_queue.rb', line 20

def self.min(array)
  new(array){ |x, y| x < y }
end

Instance Method Details

#empty? ⇒ Boolean

Returns true if the heap is empty.

Returns:

  • (Boolean) 


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# File 'lib/priority_queue.rb', line 60

def empty?
  @heap.empty?
end

#get ⇒ Object Also known as: top, first

Get the element with the highest priority.



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# File 'lib/priority_queue.rb', line 52

def get
  @heap[0]
end

#pop ⇒ Object

Pop the element with the highest priority.



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# File 'lib/priority_queue.rb', line 41

def pop
  latest = @heap.pop
  return latest if empty?

  ret_item = heap[0]
  heap[0] = latest
  shift_up(0)
  ret_item
end

#push(item) ⇒ Object Also known as: <<, append

Push new element to the heap.



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# File 'lib/priority_queue.rb', line 32

def push(item)
  shift_down(0, @heap.push(item).size - 1)
  self
end

#size ⇒ Object 



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# File 'lib/priority_queue.rb', line 64

def size
  @heap.size
end

#to_s ⇒ Object 



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# File 'lib/priority_queue.rb', line 68

def to_s
  "<#{self.class}: @heap:(#{heap.join(', ')}), @comp:<#{@comp.class} #{@comp.source_location.join(':')}>>"
end