389 Find the Difference

Given two strings s and t which consist of only lowercase letters.
String t is generated by random shuffling string s and then add one more letter at a random position.
Find the letter that was added in t.
s = "abcd"
t = "abcde"
Explanation: 'e' is the letter that was added.
The Idea: Sort the strings and return the first non matching character. Otherwise return the last character of t.
Complexity: O(2nlog(n) + n) time and O(2n) space
def findTheDifference(self, s, t):
:type s: str
:type t: str
:rtype: str
s_list = sorted(s)
t_list = sorted(t)
for s_char, t_char in zip(s_list, t_list):
if s_char is not t_char:
return t_char
return t_list[-1]