class Tree::TreeNode
TreeNode Class Description
This class models the nodes for an N-ary tree data structure. The nodes are named, and have a place-holder for the node data (i.e., content of the node). The node names are required to be unique amongst the sibling/peer nodes. Note that the name is implicitly used as an ID within the data structure).
The node's content is not required to be
unique across different nodes in the tree, and can be nil
as
well.
The class provides various methods to navigate the tree, traverse the structure, modify contents of the node, change position of the node in the tree, and to make structural changes to the tree.
A node can have any number of child nodes attached to it and hence can be used to create N-ary trees. Access to the child nodes can be made in order (with the conventional left to right access), or randomly.
The node also provides direct access to its parent node as well as other superior parents in the path to root of the tree. In addition, a node can also access its sibling nodes, if present.
Note that while this implementation does not explicitly support directed graphs, the class itself makes no restrictions on associating a node's content with multiple nodes in the tree. However, having duplicate nodes within the structure is likely to cause unpredictable behavior.
Example
{include:file:examples/example_basic.rb}
@author Anupam Sengupta
Attributes
@!attribute [rw] content Content of this node. Can be nil
.
Note that there is no uniqueness constraint related to this attribute.
@see name
@!attribute [r] name
Name of this node. Expected to be unique within the tree.
Note that the name attribute really functions as an ID within the tree structure, and hence the uniqueness constraint is required.
This may be changed in the future, but for now it is best to retain unique
names within the tree structure, and use the content
attribute
for any non-unique node requirements.
If you want to change the name, you probably want to call
rename
instead.
@see content @see rename
@!attribute [r] parent Parent of this node. Will be nil
for a
root node.
Public Class Methods
Creates a new node with a name and optional content. The node name is expected to be unique within the tree.
The content can be of any type, and defaults to nil
.
@param [Object] name Name of the node. Conventional usage is to pass a
String (Integer names may cause *surprises*)
@param [Object] content Content of the node.
@raise [ArgumentError] Raised if the node name is empty.
@note If the name is an Integer
, then the semantics of {#[]}
access
method can be surprising, as an +Integer+ parameter to that method normally acts as an index to the children array, and follows the _zero-based_ indexing convention.
@see []
# File lib/tree.rb, line 217 def initialize(name, content = nil) raise ArgumentError, "Node name HAS to be provided!" if name == nil @name, @content = name, content if name.kind_of?(Integer) warn StandardWarning, "Using integer as node name." " Semantics of TreeNode[] may not be what you expect!" " #{name} #{content}" end self.set_as_root! @children_hash = Hash.new @children = [] end
Public Instance Methods
Convenience synonym for {Tree::TreeNode#add} method.
This method allows an easy mechanism to add node hierarchies to the tree on a given path via chaining the method calls to successive child nodes.
@example Add a child and grand-child to the root
root << child << grand_child
@param [Tree::TreeNode] child the child node to add.
@return [Tree::TreeNode] The added child node.
@see #add
# File lib/tree.rb, line 333 def <<(child) add(child) end
Provides a comparision operation for the nodes.
Comparision is based on the natural ordering of the node name objects.
@param [Tree::TreeNode] other The other node to compare against.
@return [Integer] +1 if this node is a 'successor', 0 if equal and -1 if
this node is a 'predecessor'.
# File lib/tree.rb, line 926 def <=>(other) return +1 if other == nil self.name <=> other.name end
Returns the requested node from the set of immediate children.
-
If the
name
argument is an Integer, then the in-sequence array of children is accessed using the argument as the index (zero-based). However, if the second optionalnum_as_name
argument istrue
, then thename
is used literally as a name, and NOT as an index -
If the
name
argument is NOT an Integer, then it is taken to be the name of the child node to be returned.
If a non-Integer
name
is passed, and the
num_as_name
parameter is also true
, then a
warning is thrown (as this is a redundant use of the
num_as_name
flag.)
@param [String|Number] name_or_index Name of the child, or its
positional index in the array of child nodes.
@param [Boolean] num_as_name Whether to treat the Integer
+name+ argument as an actual name, and *NOT* as an _index_ to the children array.
@return [Tree::TreeNode] the requested child node. If the index
in not in range, or the name is not present, then a +nil+ is returned.
@note The use of Integer
names is allowed by using the
optional
+num_as_name+ flag.
@raise [ArgumentError] Raised if the name_or_index
argument is
nil
.
@see add @see initialize
# File lib/tree.rb, line 606 def [](name_or_index, num_as_name=false) raise ArgumentError, "Name_or_index needs to be provided!" if name_or_index == nil if name_or_index.kind_of?(Integer) and not num_as_name @children[name_or_index] else if num_as_name and not name_or_index.kind_of?(Integer) warn StandardWarning, "Redundant use of the `num_as_name` flag for non-integer node name" end @children_hash[name_or_index] end end
Adds the specified child node to this node.
This method can also be used for grafting a subtree into this node's tree, if the specified child node is the root of a subtree (i.e., has child nodes under it).
this node becomes parent of the node passed in as the argument, and the child is added as the last child (“right most”) in the current set of children of this node.
Additionally you can specify a insert position. The new node will be inserted BEFORE that position. If you don't specify any position the node will be just appended. This feature is provided to make implementation of node movement within the tree very simple.
If an insertion position is provided, it needs to be within the valid range of:
-children.size..children.size
This is to prevent nil
nodes being created as children if a
non-existant position is used.
If the new node being added has an existing parent node, then it will be removed from this pre-existing parent prior to being added as a child to this node. I.e., the child node will effectively be moved from its old parent to this node. In this situation, after the operation is complete, the node will no longer exist as a child for its old parent.
@param [Tree::TreeNode] child The child node to add.
@param [optional, Number] at_index The optional position where the node is
to be inserted.
@return [Tree::TreeNode] The added child node.
@raise [RuntimeError] This exception is raised if another child node with
the same name exists, or if an invalid insertion position is specified.
@raise [ArgumentError] This exception is raised if a nil
node
is passed
as the argument.
@see <<
# File lib/tree.rb, line 381 def add(child, at_index = -1) # Only handles the immediate child scenario raise ArgumentError, "Attempting to add a nil node" unless child raise ArgumentError, "Attempting add node to itself" if self.equal?(child) raise ArgumentError, "Attempting add root as a child" if child.equal?(root) # Lazy mans unique test, won't test if children of child are unique in # this tree too. raise "Child #{child.name} already added!" if @children_hash.include?(child.name) child.parent.remove! child if child.parent # Detach from the old parent if insertion_range.include?(at_index) @children.insert(at_index, child) else raise "Attempting to insert a child at a non-existent location" " (#{at_index}) " "when only positions from " "#{insertion_range.min} to #{insertion_range.max} exist." end @children_hash[child.name] = child child.parent = self return child end
Performs breadth-first traversal of the (sub)tree rooted at this node. The traversal at a given level is from left-to-right. this node itself is the first node to be traversed.
@yieldparam node [Tree::TreeNode] Each node.
@see preordered_each @see breadth_each
@return [Tree::TreeNode] this node, if a block if given @return [Enumerator] an enumerator on this tree, if a block is not given
# File lib/tree.rb, line 711 def breadth_each(&block) return self.to_enum(:breadth_each) unless block_given? node_queue = [self] # Create a queue with self as the initial entry # Use a queue to do breadth traversal until node_queue.empty? node_to_traverse = node_queue.shift yield node_to_traverse # Enqueue the children from left to right. node_to_traverse.children { |child| node_queue.push child } end return self if block_given? end
An array of all the immediate children of this node. The child nodes are ordered “left-to-right” in the returned array.
If a block is given, yields each child node to the block traversing from left to right.
@yieldparam child [Tree::TreeNode] Each child node.
@return [Tree::TreeNode] This node, if a block is given
@return [Array<Tree::TreeNode>] An array of the child nodes, if no block
is given.
# File lib/tree.rb, line 739 def children if block_given? @children.each {|child| yield child} return self else return @children.clone end end
Returns a copy of this node, with its parent and children links removed. The original node remains attached to its tree.
@return [Tree::TreeNode] A copy of this node.
# File lib/tree.rb, line 237 def detached_copy self.class.new(@name, @content ? @content.clone : nil) end
Returns a copy of entire (sub-)tree from this node.
@author Vincenzo Farruggia @since 0.8.0
@return [Tree::TreeNode] A copy of (sub-)tree from this node.
# File lib/tree.rb, line 247 def detached_subtree_copy new_node = detached_copy children { |child| new_node << child.detached_subtree_copy } new_node end
Traverses each node (including this node) of the (sub)tree rooted at this node by yielding the nodes to the specified block.
The traversal is depth-first and from left-to-right in pre-ordered sequence.
@yieldparam node [Tree::TreeNode] Each node.
@see preordered_each @see breadth_each
@return [Tree::TreeNode] this node, if a block if given @return [Enumerator] an enumerator on this tree, if a block is not given
# File lib/tree.rb, line 634 def each(&block) # :yields: node return self.to_enum unless block_given? node_stack = [self] # Start with this node until node_stack.empty? current = node_stack.shift # Pop the top-most node if current # Might be 'nil' (esp. for binary trees) yield current # and process it # Stack children of the current node at top of the stack node_stack = current.children.concat(node_stack) end end return self if block_given? end
Yields every leaf node of the (sub)tree rooted at this node to the specified block.
May yield this node as well if this is a leaf node. Leaf traversal is depth-first and left-to-right.
@yieldparam node [Tree::TreeNode] Each leaf node.
@see each @see breadth_each
@return [Tree::TreeNode] this node, if a block if given @return [Array<Tree::TreeNode>] An array of the leaf nodes
# File lib/tree.rb, line 761 def each_leaf &block if block_given? self.each { |node| yield(node) if node.is_leaf? } return self else self.select { |node| node.is_leaf?} end end
First child of this node. Will be nil
if no children are
present.
@return [Tree::TreeNode] The first child, or nil
if none is
present.
# File lib/tree.rb, line 778 def first_child children.first end
First sibling of this node. If this is the root node, then returns itself.
'First' sibling is defined as follows:
- First sibling
-
The left-most child of this node's parent, which may be
this node itself
@return [Tree::TreeNode] The first sibling node.
@see is_first_sibling? @see last_sibling
# File lib/tree.rb, line 804 def first_sibling is_root? ? self : parent.children.first end
Freezes all nodes in the (sub)tree rooted at this node.
The nodes become immutable after this operation. In effect, the entire tree's structure and contents become read-only and cannot be changed.
# File lib/tree.rb, line 565 def freeze_tree! each {|node| node.freeze} end
@!attribute [r] has_children? true
if the this node has any
child node.
@return [Boolean] true
if child nodes exist.
@see is_leaf?
# File lib/tree.rb, line 193 def has_children? @children.length != 0 end
@!attribute [r] has_content? true
if this node has content.
@return [Boolean] true
if the node has content.
# File lib/tree.rb, line 152 def has_content? @content != nil end
Returns true
if this node is the first sibling at its level.
@return [Boolean] true
if this is the first sibling.
@see is_last_sibling? @see first_sibling
# File lib/tree.rb, line 814 def is_first_sibling? first_sibling == self end
Returns true
if this node is the last sibling at its level.
@return [Boolean] true
if this is the last sibling.
@see is_first_sibling? @see last_sibling
# File lib/tree.rb, line 840 def is_last_sibling? last_sibling == self end
@!attribute [r] is_leaf? true
if this node is a leaf
- i.e., one without any children.
@return [Boolean] true
if this is a leaf node.
@see has_children?
# File lib/tree.rb, line 163 def is_leaf? !has_children? end
true
if this node is the only child of its parent.
As a special case, a root node will always return true
.
@return [Boolean] true
if this is the only child of its
parent.
@see siblings
# File lib/tree.rb, line 878 def is_only_child? is_root? ? true : parent.children.size == 1 end
@!attribute [r] is_root? Returns true
if this is a root node.
Note that orphaned children will also be reported as root nodes.
@return [Boolean] true
if this is a root node.
# File lib/tree.rb, line 144 def is_root? @parent.nil? end
Last child of this node. Will be nil
if no children are
present.
@return [Tree::TreeNode] The last child, or nil
if none is
present.
# File lib/tree.rb, line 786 def last_child children.last end
Last sibling of this node. If this is the root node, then returns itself.
'Last' sibling is defined as follows:
- Last sibling
-
The right-most child of this node's parent, which may be
this node itself
@return [Tree::TreeNode] The last sibling node.
@see is_last_sibling? @see first_sibling
# File lib/tree.rb, line 830 def last_sibling is_root? ? self : parent.children.last end
Returns a marshal-dump represention of the (sub)tree rooted at this node.
# File lib/tree.rb, line 261 def marshal_dump self.collect { |node| node.create_dump_rep } end
Loads a marshalled dump of a tree and returns the root node of the reconstructed tree. See the Marshal class for additional details.
@todo This method probably should be a class method. It currently clobbers
self and makes itself the root.
# File lib/tree.rb, line 285 def marshal_load(dumped_tree_array) nodes = { } dumped_tree_array.each do |node_hash| name = node_hash[:name] parent_name = node_hash[:parent] content = Marshal.load(node_hash[:content]) if parent_name then nodes[name] = current_node = Tree::TreeNode.new(name, content) nodes[parent_name].add current_node else # This is the root node, hence initialize self. initialize(name, content) nodes[name] = self # Add self to the list of nodes end end end
Next sibling for this node. The next node is defined as the node to right of this node.
Will return nil
if no subsequent node is present, or if this
is a root node.
@return [Tree::treeNode] the next sibling node, if present.
@see previous_sibling @see siblings
# File lib/tree.rb, line 892 def next_sibling return nil if is_root? myidx = parent.children.index(self) parent.children.at(myidx + 1) if myidx end
@!attribute [r] parentage An array of ancestors of this node in reversed order (the first element is the immediate parent of this node).
Returns nil
if this is a root node.
@return [Array<Tree::TreeNode>] An array of ancestors of this node @return [nil] if this is a root node.
# File lib/tree.rb, line 175 def parentage return nil if is_root? parentage_array = [] prev_parent = self.parent while (prev_parent) parentage_array << prev_parent prev_parent = prev_parent.parent end parentage_array end
Traverses the (sub)tree rooted at this node in post-ordered sequence.
@yieldparam node [Tree::TreeNode] Each node.
@see preordered_each @see breadth_each @return [Tree::TreeNode] this node, if a block if given @return [Enumerator] an enumerator on this tree, if a block is not given
# File lib/tree.rb, line 674 def postordered_each(&block) return self.to_enum(:postordered_each) unless block_given? # Using a marked node in order to skip adding the children of nodes that # have already been visited. This allows the stack depth to be controlled, # and also allows stateful backtracking. markednode = Struct.new(:node, :visited) node_stack = [markednode.new(self, false)] # Start with self until node_stack.empty? peek_node = node_stack[0] if peek_node.node.has_children? and not peek_node.visited peek_node.visited = true # Add the children to the stack. Use the marking structure. marked_children = peek_node.node.children.map {|node| markednode.new(node, false)} node_stack = marked_children.concat(node_stack) next else yield node_stack.shift.node # Pop and yield the current node end end return self if block_given? end
Traverses the (sub)tree rooted at this node in pre-ordered sequence. This is a synonym of {Tree::TreeNode#each}.
@yieldparam node [Tree::TreeNode] Each node.
@see each @see breadth_each
@return [Tree::TreeNode] this node, if a block if given @return [Enumerator] an enumerator on this tree, if a block is not given
# File lib/tree.rb, line 662 def preordered_each(&block) # :yields: node each(&block) end
Previous sibling of this node. Previous node is defined to be the node to left of this node.
Will return nil
if no predecessor node is present, or if this
is a root node.
@return [Tree::treeNode] the previous sibling node, if present.
@see next_sibling @see siblings
# File lib/tree.rb, line 909 def previous_sibling return nil if is_root? myidx = parent.children.index(self) parent.children.at(myidx - 1) if myidx && myidx > 0 end
Pretty prints the (sub)tree rooted at this node.
@param [Integer] level The indentation level (4 spaces) to start with. @param [Integer] max_depth optional maximum depth at which the printing
with stop.
@param [Proc] block optional block to use for rendering
# File lib/tree.rb, line 937 def print_tree(level = 0, max_depth = nil, block = lambda { |node, prefix| puts "#{prefix} #{node.name}" }) prefix = '' if is_root? prefix << '*' else prefix << '|' unless parent.is_last_sibling? prefix << (' ' * (level - 1) * 4) prefix << (is_last_sibling? ? '+' : '|') prefix << '---' prefix << (has_children? ? '+' : '>') end block.call(self, prefix) # Exit if the max level is defined, and reached. return unless max_depth.nil? || level < max_depth children { |child| child.print_tree(level + 1, max_depth, block) if child } # Child might be 'nil' end
Removes the specified child node from this node.
This method can also be used for pruning a sub-tree, in cases where the removed child node is the root of the sub-tree to be pruned.
The removed child node is orphaned but accessible if an alternate reference exists. If accessible via an alternate reference, the removed child will report itself as a root node for its sub-tree.
@param [Tree::TreeNode] child The child node to remove.
@return [Tree::TreeNode] The removed child node, or nil
if a
nil
was passed in as argument.
@see remove_from_parent! @see remove_all!
# File lib/tree.rb, line 501 def remove!(child) return nil unless child @children_hash.delete(child.name) @children.delete(child) child.set_as_root! child end
Removes all children from this node. If an independent reference exists to the child nodes, then these child nodes report themselves as roots after this operation.
@return [Tree::TreeNode] this node (self
)
@see remove! @see remove_from_parent!
# File lib/tree.rb, line 544 def remove_all! @children.each { |child| child.set_as_root! } @children_hash.clear @children.clear self end
Removes this node from its parent. This node becomes the new root for its subtree.
If this is the root node, then does nothing.
@return [Tree:TreeNode] self
(the removed node) if the
operation is
successful, +nil+ otherwise.
@see remove_all!
# File lib/tree.rb, line 532 def remove_from_parent! @parent.remove!(self) unless is_root? end
Renames the node and updates the parent's reference to it
@param [Object] new_name Name of the node. Conventional usage is to pass a
String (Integer names may cause *surprises*)
@return [Object] The old name
# File lib/tree.rb, line 426 def rename(new_name) old_name = @name if is_root? self.name=(new_name) else @parent.rename_child old_name, new_name end old_name end
Renames the specified child node
@param [Object] old_name old Name of the node. Conventional usage is to
pass a String (Integer names may cause *surprises*)
@param [Object] new_name new Name of the node. Conventional usage is to
pass a String (Integer names may cause *surprises*)
# File lib/tree.rb, line 445 def rename_child(old_name, new_name) raise ArgumentError, "Invalid child name specified: #{old_name}" unless @children_hash.has_key?(old_name) @children_hash[new_name] = @children_hash.delete(old_name) @children_hash[new_name].name=(new_name) end
Replaces the specified child node with another child node on this node.
@param [Tree::TreeNode] old_child The child node to be replaced. @param [Tree::TreeNode] new_child The child node to be replaced with.
@return [Tree::TreeNode] The removed child node
# File lib/tree.rb, line 469 def replace!(old_child, new_child) child_index = @children.find_index(old_child) old_child = remove! old_child add new_child, child_index return old_child end
Replaces the node with another node
@param [Tree::TreeNode] node The node to replace this node with
@return [Tree::TreeNode] The replaced child node
# File lib/tree.rb, line 483 def replace_with(node) @parent.replace!(self, node) end
@!attribute [r] root Root node for the (sub)tree to which this node belongs. A root node's root is itself.
@return [Tree::TreeNode] Root of the (sub)tree.
# File lib/tree.rb, line 133 def root root = self root = root.parent while !root.is_root? root end
An array of siblings for this node. This node is excluded.
If a block is provided, yields each of the sibling nodes to the block. The
root always has nil
siblings.
@yieldparam sibling [Tree::TreeNode] Each sibling node.
@return [Array<Tree::TreeNode>] Array of siblings of this node. Will
return an empty array for *root*
@return [Tree::TreeNode] This node, if no block is given
@see first_sibling @see last_sibling
# File lib/tree.rb, line 858 def siblings if block_given? parent.children.each { |sibling| yield sibling if sibling != self } return self else return [] if is_root? siblings = [] parent.children {|my_sibling| siblings << my_sibling if my_sibling != self} siblings end end
Returns string representation of this node. This method is primarily meant for debugging purposes.
@return [String] A string representation of the node.
# File lib/tree.rb, line 310 def to_s "Node Name: #{@name}" + " Content: " + (@content.to_s || "<Empty>") + " Parent: " + (is_root?() ? "<None>" : @parent.name.to_s) + " Children: #{@children.length}" + " Total Nodes: #{size()}" end
Protected Instance Methods
Protected method to set the name of this node. This method should NOT be invoked by client code.
@param [Object] new_name The node Name to set.
@return [Object] The new name.
# File lib/tree.rb, line 459 def name=(new_name) @name = new_name end
Private Instance Methods
Return a range of valid insertion positions. Used in the add method.
# File lib/tree.rb, line 412 def insertion_range max = @children.size min = -(max+1) min..max end