Question

I’m writing a Ruby script and would like to use a n-ary tree data structure.

Is there a good implementation that is available as source code? Thanks.

Answer 1

To expand on Otto’s answer, an easy way of getting a Hash to auto-vivify arrays is to use the default value block with Hash::new, like so:

node_children = Hash.new { |_node_children, node_key| _node_children[node_key] = [] } 

But really, the code depends on what you want to do with your arrays. You can either set them up with Hashes and Arrays, or make some classes:

class Node     attr_accessor :value, :children     def initialize(value, children=[])         @value = value         @children = children     end     def to_s(indent=0)         value_s = @value.to_s         sub_indent = indent + value_s.length         value_s + @children.map { |child| ' - ' + child.to_s(sub_indent + 3) }.join('\n' + ' ' * sub_indent)     end end  ROOT = Node.new('root', %w{ farleft left center right farright }.map { |str| Node.new(str) } ) puts 'Original Tree' puts ROOT puts  ROOT.children.each do |node|      node.children = %w{ one two three four }.map { |str| Node.new(node.value + ':' + str) } end puts 'New Tree' puts ROOT puts 

This code, for example, gives:

Original Tree root - farleft      - left      - center      - right      - farright  New Tree root - farleft - farleft:one                - farleft:two                - farleft:three                - farleft:four      - left - left:one             - left:two             - left:three             - left:four      - center - center:one               - center:two               - center:three               - center:four      - right - right:one              - right:two              - right:three              - right:four      - farright - farright:one                 - farright:two                 - farright:three                 - farright:four