recursion test

def find_pairs(input, sum, results = [])
  return results.uniq if input.empty? # break condition

  input.each_with_index do |element, i|
    input.delete_at(i) # reduces the array size for already tried element
    other_element = sum - element
    index = input.index(other_element) # find other element index
    if index.present?
      input.delete_at(index) # reduces the array size for already tried element
      pair = element > other_element ? [other_element, element] : [element, other_element]
      results << pair
    end
    find_pairs(input, sum, results) # recursion
  end
end