Turning a Hash of Arrays into an Array of Hashes in Ruby

Question

We have the following datastructures:

{:a => [\"val1\", \"val2\"], :b => [\"valb1\", \"valb2\"], ...}

And I want to turn that into

Answer 1

This solution works with arbitrary numbers of values (val1, val2...valN):

{:a => ["val1", "val2"], :b => ["valb1", "valb2"]}.inject([]){|a, (k,vs)| 
  vs.each_with_index{|v,i| (a[i] ||= {})[k] = v} 
  a
}
# => [{:a=>"val1", :b=>"valb1"}, {:a=>"val2", :b=>"valb2"}]

[{:a=>"val1", :b=>"valb1"}, {:a=>"val2", :b=>"valb2"}].inject({}){|a, h| 
  h.each_pair{|k,v| (a[k] ||= []) << v}
  a
}
# => {:a=>["val1", "val2"], :b=>["valb1", "valb2"]}