A simple implementation of nodes in a tree. Each tree can have arbitrarily many child nodes.

treenode.rb

class TreeNode
  attr_accessor :parent, :children 
  attr_reader :value

  def initialize(value)
    @value = value
    @parent = nil
    @children = []
  end

  def children=(array)
    # Accepts an array of TreeNode instances, or an array of values
    # you wish to create nodes for.
    @children = array
    @children.map!{|val| TreeNode.new(val)} if !array[0].is_a? TreeNode
    @children.each { |node| node.parent = self }
  end

  def dfs(target_value)
  # Depth-first search.  Returns TreeNode instance
  # with target value, or nil if not in tree.  
    return self if @value == target_value

    found_node = nil 
    @children.each do |child|
      found_node = child.dfs(target_value)
      return found_node unless found_node.nil?
    end
    
    found_node
  end

  def path
    # returns an array of TreeNode instances 
    # from self to the tree root.
    path = [self]
    current_node = self
    until current_node.parent.nil? # root's parent is nil
      path << current_node.parent
      current_node = current_node.parent
    end
    path.reverse
  end

end