Converting a hash into a nested hash

Question

This question is the inverse of this question.

Given a hash that has an array for each key like

{
    [:a, :b, :c] => 1,
    [:a, :b, :d] => 2,         


        

Answer 1

Another way:

def convert(h)
  h.each_with_object({}) { |(a,n),f| f.update({ a.first=>(a.size==1 ? n :
    convert({ a[1..-1]=>n })) }) { |_,ov,nv| ov.merge(nv) } }
end

Try it:

h = {
    [:a, :b, :c] => 1,
    [:a, :b, :d] => 2,
    [:a, :e] => 3,
    [:f] => 4,
}

convert(h) #=> {:a=>{:b=>{:d=>2}, :e=>3},
           #    :f=>4}