Ruby：在树表示中转换平面数组

Question

我正在尝试编写一个函数来将带有路径信息的平面数组转换为该数组的树表示。

我们的目标是把一个数组变成如下：

[
{ :name => "a", :path => [ 'a' ] },
{ :name => "b", :path => [ 'a', 'b' ] },
{ :name => "c", :path => [ 'a', 'b', 'c' ] },
{ :name => "d", :path => [ 'a', 'd' ] },
{ :name => "e", :path => [ 'e' ] }
]

变成这样：

[{:node=>{:name=>"a", :path=>["a"]},
  :children=>
   [{:node=>{:name=>"b", :path=>["a", "b"]},
     :children=>
      [{:node=>{:name=>"c", :path=>["a", "b", "c"]}, :children=>[]}]},
    {:node=>{:name=>"d", :path=>["a", "d"]}, :children=>[]}]},
 {:node=>{:name=>"e", :path=>["e"]}, :children=>[]}]

我得到的最接近的结果是使用以下代码：

class Tree

  def initialize
    @root = { :node => nil, :children => [ ] } 
  end 

  def from_array( array )
    array.inject(self) { |tree, node| tree.add(node) }
    @root[:children]
  end 

  def add(node)
    recursive_add(@root, node[:path].dup, node)
    self
  end 

  private

  def recursive_add(parent, path, node)
    if(path.empty?)
      parent[:node] = node
      return
    end 
    current_path = path.shift
    children_nodes = parent[:children].find { |child| child[:node][:path].last == current_path } 
    unless children_nodes
      children_nodes = { :node => nil, :children => [ ] } 
      parent[:children].push children_nodes
    end 
    recursive_add(children_nodes, path, node)
  end 
end

flat = [ 
  { :name => "a", :path => [ 'a' ] },
  { :name => "b", :path => [ 'a', 'b' ] },
  { :name => "c", :path => [ 'a', 'b', 'c' ] },
  { :name => "d", :path => [ 'a', 'd' ] },
  { :name => "e", :path => [ 'e' ] } 
]

require 'pp'
pp Tree.new.from_array( flat )

但它非常冗长，我觉得它对于非常大的集合可能不是很有效。

在 ruby​​ 中实现这一目标的最简洁和最有效的方法是什么？

Answer 1

这是我的尝试。

array = [
{ :name => "a", :path => [ 'a' ] },
{ :name => "b", :path => [ 'a', 'b' ] },
{ :name => "c", :path => [ 'a', 'b', 'c' ] },
{ :name => "d", :path => [ 'a', 'd' ] },
{ :name => "e", :path => [ 'e' ] }
]

array
.sort_by{|h| -h[:path].length}
.map{|h| {node: h, children: []}}
.tap{|array| 
  while array.first[:node][:path].length > 1
    child = array.shift
    array
    .find{|h| h[:node][:name] == child[:node][:path][-2]}[:children]
    .push(child)
  end
}

# => [
  {:node=>{:name=>"e", :path=>["e"]}, :children=>[]},
  {:node=>{:name=>"a", :path=>["a"]}, :children=>[
    {:node=>{:name=>"d", :path=>["a", "d"]}, :children=>[]},
    {:node=>{:name=>"b", :path=>["a", "b"]}, :children=>[
      {:node=>{:name=>"c", :path=>["a", "b", "c"]}, :children=>[]}
    ]}
  ]}
]