Interview Questions -- 1

interview_1.rb

# I liked this interview question. It fit nicely in about an hour, and I 
# think I'd consider re-using it. It isn't too gimmicky and it's not one 
# of those "did you do a CS degree" tests, which help nobody.
#
# Q: given a json input in the form of a set of jobs and subjobs:
#  
# '[
#   {"id":"1","name":"Designer","parent_id":null},
#   {"id":"2","name":"Engineer","parent_id":null},
#   {"id":"3","name":"Software Engineer","parent_id":"2"},
#   {"id":"7","name":"UX Designer","parent_id":"1"},
#   {"id":"6","name":"UI Designer","parent_id":"1"},
#   {"id":"5","name":"FrontEnd Engineer","parent_id":"3"},
#   {"id":"4","name":"Backend Engineer","parent_id":"3"}
# ]'
#
# we want an output that shows jobs and subjobs thus:
#
# Designer
# -UI Designer
# -UX Designer
# Engineer
# -Software Engineer
# --Backend Engineer
# --FrontEnd Engineer
#
# In the live interview I did this as a set of methods called at the end, 
# but with a few mins to think about it a quick refactor gives me this
# as my solution:

module Helpers
  def sorted(arr)
    arr.sort { |a,b| a.name <=> b.name }
  end
end

class Element
  include Helpers
  attr_reader :children, :id, :parent_id, :name

  def self.from(element_hashes)
    element_hashes.map do |ele|
      new(id: ele["id"], parent_id: ele["parent_id"], name: ele["name"])
    end
  end

  def initialize(id:, parent_id:, name:)
    @id = id
    @parent_id = parent_id
    @name = name
    @children = []
  end

  def add_child(element)
    children << element
  end

  def claim_children!(array)
    child_candidates.each do |candidate|
      add_child if (candidate.parent_id == id)
    end
    self
  end

  def print(leader="")
    puts leader + name
    unless children.empty?
      sorted(children).each do |child|
        child.print(leader + "-")
      end
    end
  end
end

class Tree
  include Helpers
  attr_reader :element_array, :element_tree, :roots

  def self.from(array)
    new.tap  { |t| t.build_from(array) }
  end

  def initialize
    @element_array = []
    @element_tree = []
    @roots = []
  end

  def build_from(array)
    @element_array = array
    claim_children!
    self
  end

  def print
    return if roots.empty?
    sorted(roots).each(&:print)
  end


  private

  def claim_children!
    element_array.each do |element|
      element.claim_children(element_array - [element])
      element_tree << element
      roots << element if element.parent_id.nil?
    end
  end
end

def print_roles
  elements = Element.from(@roles)
  tree = Tree.from(elements)
  tree.print
  nil
end

# $ require 'json'
# => true

# $ @roles = JSON.parse([json-array-above])
# => [{"id"=>"1", "name"=>"Designer", "parent_id"=>nil}, {"id"=>"2", "name"=>"Engineer", "parent_id"=>nil}, 
#    {"id"=>"3", "name"=>"Software Engineer", "parent_id"=>"2"}, {"id"=>"7", "name"=>"UX Designer", "parent_id"=>"1"}, 
#    {"id"=>"6", "name"=>"UI Designer", "parent_id"=>"1"}, {"id"=>"5", "name"=>"FrontEnd Engineer", "parent_id"=>"3"}, 
#    {"id"=>"4", "name"=>"Backend Engineer", "parent_id"=>"3"}]

# $ print_roles
# Designer
# -UI Designer
# -UX Designer
# Engineer
# -Software Engineer
# --Backend Engineer
# --FrontEnd Engineer
# => nil