class Containers::PriorityQueue
rdoc
A Priority Queue is a data structure that behaves like a queue except that elements have an associated priority. The #next and #pop methods return the item with the next highest priority. Priority Queues are often used in graph problems, such as Dijkstra's Algorithm for shortest path, and the A* search algorithm for shortest path. This container is implemented using the Fibonacci heap included in the Collections library. MIT License Copyright (c) 2009 Kanwei Li Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Public Class Methods
new(&block)
click to toggle source
Create a new, empty PriorityQueue
# File lib/containers/priority_queue.rb, line 38 def initialize(&block) # We default to a priority queue that returns the largest value block ||= lambda { |x, y| (x <=> y) == 1 } @heap = Containers::Heap.new(&block) end
Public Instance Methods
clear()
click to toggle source
Clears all the items in the queue.
# File lib/containers/priority_queue.rb, line 65 def clear @heap.clear end
delete(priority) → object
click to toggle source
delete(priority) → nil
Delete an object with specified priority from the queue. If there are duplicates, an arbitrary object with that priority is deleted and returned. Returns nil if there are no objects with the priority.
q = PriorityQueue.new q.push("Alaska", 50) q.push("Delaware", 30) q.delete(50) #=> "Alaska" q.delete(10) #=> nil
# File lib/containers/priority_queue.rb, line 131 def delete(priority) @heap.delete(priority) end
empty?()
click to toggle source
Returns true if the queue is empty, false otherwise.
# File lib/containers/priority_queue.rb, line 70 def empty? @heap.empty? end
has_priority? priority → boolean
click to toggle source
Return true if the priority is in the queue, false otherwise.
q = PriorityQueue.new q.push("Alaska", 1) q.has_priority?(1) #=> true q.has_priority?(2) #=> false
# File lib/containers/priority_queue.rb, line 84 def has_priority?(priority) @heap.has_key?(priority) end
next → object
click to toggle source
Return the object with the next highest priority, but does not remove it
q = Containers::PriorityQueue.new q.push("Alaska", 50) q.push("Delaware", 30) q.push("Georgia", 35) q.next #=> "Alaska"
# File lib/containers/priority_queue.rb, line 98 def next @heap.next end
Alias for: pop
pop → object
click to toggle source
Return the object with the next highest priority and removes it from the queue
q = Containers::PriorityQueue.new q.push("Alaska", 50) q.push("Delaware", 30) q.push("Georgia", 35) q.pop #=> "Alaska" q.size #=> 2
# File lib/containers/priority_queue.rb, line 113 def pop @heap.pop end
Also aliased as: next!
push(object, priority)
click to toggle source
Add an object to the queue with associated priority.
q = Containers::PriorityQueue.new q.push("Alaska", 1) q.pop #=> "Alaska"
# File lib/containers/priority_queue.rb, line 60 def push(object, priority) @heap.push(priority, object) end
size()
click to toggle source
Returns the number of elements in the queue.
q = Containers::PriorityQueue.new q.size #=> 0 q.push("Alaska", 1) q.size #=> 1
# File lib/containers/priority_queue.rb, line 50 def size @heap.size end
Also aliased as: length