hash_intersection.rb

first = {"a" => 4, "b" => 1, "c" => 3, "g" => 201, "h" => 501}
second = {"d" => 19, "e" => 18, "c" => 17, "g" => 201, "h" => 501}

keys_intersection = first.keys & second.keys
merged = first.dup.update(second)

intersection = {}
keys_intersection.each do |k|
  intersection[k]=merged[k] unless first[k] != second[k]
end

# same thing as freedom patch

class Hash
  def intersection(another_hash)
    keys_intersection = self.keys & another_hash.keys
    merged = self.dup.update(another_hash)

    intersection = {}
    keys_intersection.each {|k| intersection[k] = merged [k] unless self[k] != another_hash[k]}
    intersection
  end
end

{"a" => 4, "b" => 1, "c" => 3, "g" => 201, "h" => 501}.intersection({"d" => 19, "e" => 18, "c" => 17, "g" => 201, "h" => 501})
 => {"g"=>201, "h"=>501}