message: solution update
diff: # Time: O(n)
  -# Space: O(n)
  +# Space: O(1)
  class Solution(object):
  def reverseString(self, s):
  @@ -7,22 +7,10 @@ class Solution(object):
  :type s: str
  :rtype: str
  """
  - string = list(s)
  - i, j = 0, len(string) - 1
  + i, j = 0, len(s) - 1
  while i < j:
  - string[i], string[j] = string[j], string[i]
  + s[i], s[j] = s[j], s[i]
  i += 1
  j -= 1
  - return "".join(string)
  -
  -
  -# Time: O(n)
  -# Space: O(n)
  -class Solution2(object):
  - def reverseString(self, s):
  - """
  - :type s: str
  - :rtype: str
  - """
  - return s[::-1]
  + return s
  