Finding unique pairs in array

test.rb

# 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 Test
  def remove_used(match, array)
    array.delete_at array.index match[0]
    array.delete_at array.index match[1]
    array
  end

  def find_matching_from_array_for_val(val, array)
    array.each_with_index do |compare, index|
      return [val,compare] if equal_100?(val, compare)
    end
    nil
  end

  def equal_100?(val1, val2)
    val1 + val2 == 100
  end

  def perform(array)
    # p array
    output = Array.new
    copy = array
    array.each_with_index do |val, index|
      break if (index + 1 >= array.size)
      match = find_matching_from_array_for_val(val, copy)
      if match
        output << match
        copy = remove_used(match, copy)
      end
    end
    output.uniq
  end
end

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

t = Test.new
result = t.perform(input)
p result