Tree

class Tree
    attr_accessor :children, :node_name

    def initialize(other={})
        if not other.nil?
            key, children = other.first
            @node_name = key;
            @children = []
            other.values.each {|x| @children << Tree.new(x)}
        end
    end

    def visit_all(&block)
        visit &block
        children.each {|c| c.visit_all &block} unless children.nil?
    end

    def visit(&block)
        block.call self
    end
end


t = Tree.new({'grandpa'=>{'dad'=>{'child1'=>{},'child2'=>{}},'uncle'=>{'child3'=>{},'child4'=>{}}}})
t.visit_all {|x| puts x.node_name}
gets