BinaryTree.rb

# O(n)
def binarytree(array, target)
  right = array[0]
  left  = array[array.length - 1]

  while right != left do
    sum = right + left
    return "find" if sum == target
    if sum > target
      left = left - 1
    else
      right = right + 1
    end
  end

  "none"
end

# main
array = [5, 2, 0, 9, 6, 1, 3, 4]
target = 9
# sort is O(n log n)
puts binarytree(array.sort, target)