class SyntaxSuggest::PriorityQueue
Holds elements in a priority heap on insert
Instead of constantly calling ‘sort!`, put the element where it belongs the first time around
Example:
queue = PriorityQueue.new queue << 33 queue << 44 queue << 1 puts queue.peek # => 44
Attributes
Public Class Methods
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# File lib/syntax_suggest/priority_queue.rb, line 22 def initialize @elements = [] end
Public Instance Methods
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# File lib/syntax_suggest/priority_queue.rb, line 26 def <<(element) @elements << element bubble_up(last_index, element) end
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# File lib/syntax_suggest/priority_queue.rb, line 42 def empty? @elements.empty? end
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# File lib/syntax_suggest/priority_queue.rb, line 98 def exchange(source, target) a = @elements[source] b = @elements[target] @elements[source] = b @elements[target] = a end
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# File lib/syntax_suggest/priority_queue.rb, line 38 def length @elements.length end
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# File lib/syntax_suggest/priority_queue.rb, line 31 def pop exchange(0, last_index) max = @elements.pop bubble_down(0) max end
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# File lib/syntax_suggest/priority_queue.rb, line 55 def sorted out = [] elements = @elements.dup while (element = pop) out << element end @elements = elements out.reverse end
Used for testing, extremely not performant
Private Instance Methods
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# File lib/syntax_suggest/priority_queue.rb, line 81 def bubble_down(index) child_index = (index * 2) + 1 return if child_index > last_index not_the_last_element = child_index < last_index left_element = @elements[child_index] right_element = @elements[child_index + 1] child_index += 1 if not_the_last_element && (right_element <=> left_element) == 1 return if (@elements[index] <=> @elements[child_index]) >= 0 exchange(index, child_index) bubble_down(child_index) end
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# File lib/syntax_suggest/priority_queue.rb, line 69 def bubble_up(index, element) return if index <= 0 parent_index = (index - 1) / 2 parent = @elements[parent_index] return if (parent <=> element) >= 0 exchange(index, parent_index) bubble_up(parent_index, element) end
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# File lib/syntax_suggest/priority_queue.rb, line 65 def last_index @elements.size - 1 end