message: Update rearrange-array-elements-by-sign.py
diff: # two pointers
  class Solution(object):
  + def rearrangeArray(self, nums):
  + """
  + :type nums: List[int]
  + :rtype: List[int]
  + """
  + pos, neg = 0, 1
  + result = [0]*len(nums)
  + for x in nums:
  + if x > 0:
  + result[pos] = x
  + pos += 2
  + else:
  + result[neg] = x
  + neg += 2
  + return result
  +
  +
  +# Time: O(n)
  +# Space: O(1)
  +# generator
  +class Solution2(object):
  def rearrangeArray(self, nums):
  """
  :type nums: List[int]
  @@ -26,7 +47,7 @@ class Solution(object):
  # Time: O(n)
  # Space: O(n)
  # array, implementation
  -class Solution2(object):
  +class Solution3(object):
  def rearrangeArray(self, nums):
  """
  :type nums: List[int]
  