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

height_black[RW]

Public Class Methods

new() click to toggle source

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

[](key)
Alias for: get
[]=(key, value)
Alias for: push
delete(key) click to toggle source

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
delete_max() click to toggle source

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
delete_min() click to toggle source

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
each() { |key, value| ... } click to toggle source

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
empty?() click to toggle source

Returns true if the tree is empty, false otherwise

# File lib/containers/rb_tree_map.rb, line 140
def empty?
  @root.nil?
end
get(key) click to toggle source

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
Also aliased as: []
has_key?(key) click to toggle source

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
height() click to toggle source

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
max_key() click to toggle source

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
min_key() click to toggle source

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
push(key, value) click to toggle source

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
Also aliased as: []=
size() click to toggle source

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

delete_max_recursive(node) click to toggle source
# 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
delete_min_recursive(node) click to toggle source
# 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
delete_recursive(node, key) click to toggle source
# 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
get_recursive(node, key) click to toggle source
# 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
insert(node, key, value) click to toggle source
# 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
isred(node) click to toggle source
# File lib/containers/rb_tree_map.rb, line 385
def isred(node)
  return false if node.nil?
  
  node.color == :red
end
max_recursive(node) click to toggle source
# 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
min_recursive(node) click to toggle source
# 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