def assert(x)
  raise x.inspect unless x
end

class Solution
  # time: O(n)
  # space: O(n)
  def self.run(items, k)
    nums = {}

    for i in (0...items.size)
      nums[items[i]] = true
      return true if nums[k - items[i]]
    end

    false
  end
end
=begin
 h
|4|7|1|-3|2|
=end

assert(Solution.run([4, 7, 1, -3, 2], 5))
assert(!Solution.run([], 5))
assert(!Solution.run([1], 5))
assert(Solution.run([1,-3,7,8], 5))
assert(Solution.run([3,1,3], 6))
puts "Yay!"