0389.py

class Solution:
    def findTheDifference(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: str
        """
        result = 0
        for ch in (s+t):
            result ^= ord(ch)

        return chr(result)
        
if __name__ == "__main__":
    s = "abcd"
    t = "abcde"
    print(Solution().findTheDifference(s, t))