unique_pairs.rb

sample_input = [0, 1, 100, 99, 0, 10, 90, 30, 55, 33, 55, 75, 50, 51, 49, 50, 51, 49, 51];

def unique_pairs(array)
  pairs = []
  array.combination(2).map do | pair |
    if pair[0] + pair[1] === 100 && !pairs.include?(pair) && !pairs.include?(pair.reverse())
      pairs << pair
    end
  end

  p pairs

end

unique_pairs(sample_input)