class Containers::RubyRBTreeMap
A RBTreeMap is a map that is stored in sorted order based on the order of its keys. This ordering is determined by applying the function <=> to compare the keys. No duplicate values for keys are allowed, so duplicate values are overwritten.
A major advantage of RBTreeMap over a Hash is the fact that keys are stored in order and can thus be iterated over in order. This is useful for many datasets.
The implementation is adapted from Robert Sedgewick's Left Leaning Red-Black Tree implementation, which can be found at www.cs.princeton.edu/~rs/talks/LLRB/Java/RedBlackBST.java
Containers::RBTreeMap automatically uses the faster C implementation if it was built when the gem was installed. Alternatively, Containers::RubyRBTreeMap and Containers::CRBTreeMap can be explicitly used as well; their functionality is identical.
Most methods have O(log n) complexity.
Attributes
Public Class Methods
Create and initialize a new empty TreeMap.
# File lib/containers/rb_tree_map.rb, line 26 def initialize @root = nil @height_black = 0 end
Public Instance Methods
Deletes the item and key if it's found, and returns the item. Returns nil if key is not present.
!!! Warning !!! There is a currently a bug in the delete method that occurs rarely but often enough, especially in large datasets. It is currently under investigation.
Complexity: O(log n)
map = Containers::TreeMap.new map.push("MA", "Massachusetts") map.push("GA", "Georgia") map.min_key #=> "GA"
# File lib/containers/rb_tree_map.rb, line 130 def delete(key) result = nil if @root @root, result = delete_recursive(@root, key) @root.color = :black if @root end result end
Deletes the item with the smallest key and returns the item. Returns nil if key is not present.
Complexity: O(log n)
map = Containers::TreeMap.new map.push("MA", "Massachusetts") map.push("GA", "Georgia") map.delete_max #=> "Georgia" map.size #=> 1
# File lib/containers/rb_tree_map.rb, line 173 def delete_max result = nil if @root @root, result = delete_max_recursive(@root) @root.color = :black if @root end result end
Deletes the item with the smallest key and returns the item. Returns nil if key is not present.
Complexity: O(log n)
map = Containers::TreeMap.new map.push("MA", "Massachusetts") map.push("GA", "Georgia") map.delete_min #=> "Massachusetts" map.size #=> 1
# File lib/containers/rb_tree_map.rb, line 154 def delete_min result = nil if @root @root, result = delete_min_recursive(@root) @root.color = :black if @root end result end
Iterates over the TreeMap from smallest to largest element. Iterative approach.
# File lib/containers/rb_tree_map.rb, line 183 def each return nil unless @root stack = Containers::Stack.new cursor = @root loop do if cursor stack.push(cursor) cursor = cursor.left else unless stack.empty? cursor = stack.pop yield(cursor.key, cursor.value) cursor = cursor.right else break end end end end
Returns true if the tree is empty, false otherwise
# File lib/containers/rb_tree_map.rb, line 140 def empty? @root.nil? end
Return the item associated with the key, or nil if none found.
Complexity: O(log n)
map = Containers::TreeMap.new map.push("MA", "Massachusetts") map.push("GA", "Georgia") map.get("GA") #=> "Georgia"
# File lib/containers/rb_tree_map.rb, line 89 def get(key) get_recursive(@root, key) end
Return true if key is found in the TreeMap, false otherwise
Complexity: O(log n)
map = Containers::TreeMap.new map.push("MA", "Massachusetts") map.push("GA", "Georgia") map.has_key?("GA") #=> true map.has_key?("DE") #=> false
# File lib/containers/rb_tree_map.rb, line 77 def has_key?(key) !get(key).nil? end
Return the height of the tree structure in the TreeMap.
Complexity: O(1)
map = Containers::TreeMap.new map.push("MA", "Massachusetts") map.push("GA", "Georgia") map.height #=> 2
# File lib/containers/rb_tree_map.rb, line 64 def height @root and @root.height or 0 end
Return the largest key in the map.
Complexity: O(log n)
map = Containers::TreeMap.new map.push("MA", "Massachusetts") map.push("GA", "Georgia") map.max_key #=> "MA"
# File lib/containers/rb_tree_map.rb, line 114 def max_key @root.nil? ? nil : max_recursive(@root) end
Return the smallest key in the map.
Complexity: O(log n)
map = Containers::TreeMap.new map.push("MA", "Massachusetts") map.push("GA", "Georgia") map.min_key #=> "GA"
# File lib/containers/rb_tree_map.rb, line 102 def min_key @root.nil? ? nil : min_recursive(@root) end
Insert an item with an associated key into the TreeMap, and returns the item inserted
Complexity: O(log n)
map = Containers::TreeMap.new map.push(“MA”, “Massachusetts”) #=> “Massachusetts” map.get(“MA”) #=> “Massachusetts”
# File lib/containers/rb_tree_map.rb, line 38 def push(key, value) @root = insert(@root, key, value) @height_black += 1 if isred(@root) @root.color = :black value end
Return the number of items in the TreeMap.
map = Containers::TreeMap.new map.push("MA", "Massachusetts") map.push("GA", "Georgia") map.size #=> 2
# File lib/containers/rb_tree_map.rb, line 52 def size @root and @root.size or 0 end
Private Instance Methods
# File lib/containers/rb_tree_map.rb, line 331 def delete_max_recursive(node) if (isred(node.left)) node = node.rotate_right end return nil, node.value if node.right.nil? if ( !isred(node.right) && !isred(node.right.left) ) node.move_red_right end node.right, result = delete_max_recursive(node.right) return node.fixup, result end
# File lib/containers/rb_tree_map.rb, line 318 def delete_min_recursive(node) if node.left.nil? return nil, node.value end if ( !isred(node.left) && !isred(node.left.left) ) node.move_red_left end node.left, result = delete_min_recursive(node.left) return node.fixup, result end
# File lib/containers/rb_tree_map.rb, line 293 def delete_recursive(node, key) if (key <=> node.key) == -1 node.move_red_left if ( !isred(node.left) && !isred(node.left.left) ) node.left, result = delete_recursive(node.left, key) else node.rotate_right if isred(node.left) if ( ( (key <=> node.key) == 0) && node.right.nil? ) return nil, node.value end if ( !isred(node.right) && !isred(node.right.left) ) node.move_red_right end if (key <=> node.key) == 0 result = node.value node.value = get_recursive(node.right, min_recursive(node.right)) node.key = min_recursive(node.right) node.right = delete_min_recursive(node.right).first else node.right, result = delete_recursive(node.right, key) end end return node.fixup, result end
# File lib/containers/rb_tree_map.rb, line 345 def get_recursive(node, key) return nil if node.nil? case key <=> node.key when 0 then return node.value when -1 then return get_recursive(node.left, key) when 1 then return get_recursive(node.right, key) end end
# File lib/containers/rb_tree_map.rb, line 369 def insert(node, key, value) return Node.new(key, value) unless node case key <=> node.key when 0 then node.value = value when -1 then node.left = insert(node.left, key, value) when 1 then node.right = insert(node.right, key, value) end node.rotate_left if (node.right && node.right.red?) node.rotate_right if (node.left && node.left.red? && node.left.left && node.left.left.red?) node.colorflip if (node.left && node.left.red? && node.right && node.right.red?) node.update_size end
# File lib/containers/rb_tree_map.rb, line 385 def isred(node) return false if node.nil? node.color == :red end
# File lib/containers/rb_tree_map.rb, line 362 def max_recursive(node) return node.key if node.right.nil? max_recursive(node.right) end
# File lib/containers/rb_tree_map.rb, line 355 def min_recursive(node) return node.key if node.left.nil? min_recursive(node.left) end