# frozen_string_literal: true

# Write a function which, given an array of integers of value greater or equal to 0, returns all unique pairs which
# sum to 100.
#
# Example data:
#
# input = [0, 1, 100, 99, 0, 10, 90, 30, 55, 33, 55, 75, 50, 51, 49, 50, 51, 49, 51]
# output = [[1,99], [0,100], [10,90], [51,49], [50,50]]
class UniquePair
  def self.unique_pairs(numbers, sum=100)
    Array(numbers)
      .combination(2)
      .map do |x, y|
        x, y = y, x if x > y
        [x, y] if x + y == sum
      end.compact.sort.uniq || []
  end
end